| 1 | Monocled cobra |
Length: 1.35-1.5m (record 230cm).
The snake species responsible for the most deaths in Thailand. Monocled cobras have an LD50 venom toxicity score of 0.23-0.37mg, which is stronger than most rattlesnakes, and a high venom yield of 263mg per bite. Monocled cobras wrap up all possible dangers into one savage package, as they have an aggressive temperament, and they commonly occur around human habitation. The only skill they lack is the ability to spit venom (except very occasionally).
Monocled cobras can appear almost anywhere. They can battle their way into a kitchen while a man brandishes a broomstick, pop out from under a fridge to bite your toe, and reappear in your backgarden no matter how many times you call reptile controllers to remove them. Every Thai resident has a monocled cobra story, whether starring themselves or a friend or relative.
Monocled cobras inhabit the vast majority of Thailand, including bustling Bangkok itself. However, they’re particularly common around the centre, and skip the far south and northeast.
The venom of monocled cobras causes both massive skin necrosis and neurotoxicity, via the powerful alpha-cobratoxin. Do not underestimate the monocled cobra in any circumstances. Remember that time is key – get yourself or loved one to a hospital as quickly as possible.
| 2 | Red-necked keelback |
Length: 60-80cm.
A semi-aquatic snake which is common all over Thailand. Red-necked keelbacks (Rhabdophis siamensis) are common in long grass near ponds, near flooded rice paddies, and even in water culverts in cities.
The red-necked keelback’s claim to fame is that until a few years ago, everyone thought they were harmless. People kept them as low-maintenance household pets, feeding and touching them happily. They lack instantly injected front fang venom like a cobra, instead secreting a venom from their rear fangs, which must slowly soak into a bite wound, via repeated chewing. Consequently, people assumed that to suffer harm, you’d have to leave the red-necked keelback attached for 2 minutes.
Slowly though, reports of life-threatening hospitalisations emerged. A child was chewed for just two seconds, and one man was chewed for 20 seconds, sending both to intensive care for a week. The venom potency was tested scientifically and proven to be 1.29mg, which is stronger than a cottonmouth, with the potential to cause brain haemorrhages and kidney failure.
Being such a recently identified villain, the red-necked keelback lacks a dedicated antivenom. They add to this danger with poison stored in their signature red neck, acquired from toxic toads they eat. These toxins are stored in special nuchal glands, which burst if people dare to touch them.
In the old days, Thai villagers walked past this snake with no worries. Unfortunately, many still do, as news is slow to trickle out and reach every obscure village and mountain community in the country.
| 3 | White-lipped pit viper |
Length: 60-90cm (max 104cm).
The Trimeresurus green pitviper family is one level below the monocled cobra in terms of pure savageness. All members have a powerful venom, and while this isn’t automatically fatal, it wreaks havoc on the human body and virtually guarantees a hospital visit.
The white-lipped pit viper (Trimeresurus albolabris) is especially notorious, as it’s the most common member in Thailand, and southeast Asia overall. This species is nearly entirely green, except for the signature white-lip, which extends all the way down their body.
The venom of Trimeresurus albolabris specialises in haemorrhaging, with possible skin tissue necrosis in severe bites. The raw potency matches the monocled cobra, at an LD50 score of 0.37mg, but the venom yield is significantly lower at 8-15mg. This lower volume is why it kills people less commonly, but deaths are still occasionally reported from Trimeresurus albolabris bites.
This brightly coloured venomous snake is usually found on branches, and has a particular tendency to pop up in gardens, including inside Bangkok itself. They can be very common locally; some reptile fanatics have found dozens inside one hour. A top situation for being bitten is doing garden work, perhaps while bending over and absentmindedly whistling a tune.
Luckily, Thai hospitals are well prepared for this species, as they nearly always stock the generic Trimeresurus green pitviper antivenom (useful for all members).
| 4 | Beautiful pitviper |
Length: 40-70cm.
It’s called the beautiful pit viper. Big surprise to hear then, that this jungle snake has a nasty venom which it doesn’t mind unleashing on innocent people.
The beautiful pitviper (Trimeresurus venustus) is the significantly less common cousin of the white-lipped pitviper, appearing in pristine forests rather than towns and cities. You won’t find this snake in Bangkok, as it lives only in southern Thailand, in the province of Chumphon southwards. It’s particularly common in Tai Rom Yen National Park, a mountainous jungle landscape where a thick mist lies all year around.
Trimeresurus venustus is covered with alternating red and green patterns, which create an exotic tapestry of colours, along with supreme camouflage. For years, there was very little toxinology data for this species. However, in a case reported in 2019, a 60 year old snake breeder made a bold leap for snake science when he was bitten on the middle finger, while removing a beautiful pit viper from a feeding box. The finger became painful and swollen, and within one hour this had spread to the rest of his hand.
Doctors soon arrived on the scene, and administered antibiotics and analgesics, which prevented the normal bleeding and coagulopathy of pitviper species. The man was discharged after 26 hours. The incident was no laughing matter, but the beautiful pitviper may be one of the safer of Thailand’s 17 green pitvipers.
| 5 | MacLelland’s coral snake |
Length: 40-80cm.
There are 5 coral snakes in Thailand, but MacLelland’s coral snake stands apart as the only native member of the Sinomicrurus family. This species is found in central and northwestern areas of Thailand, and moves mainly by night.
MacLelland’s coral snake hunts slowly and deliberately, shifting patiently through leaf litter on the forest floor. It’s a silly looking snake, with a dull red body, and a head with such contrasting white and black colours that it looks like a road construction worker has painted them. Its head is so flat that it seems to have been stepped on.
MacLelland’s coral snake (Sinomicrurus macclellandi) could never intimidate you with its facial expressions; the viciousness of a monocled cobra is far away. But despite all that, this species has venom so potent that it’s rumoured to cause instant heart failure. Like other coral snakes, MacLelland’s coral snake spews out neurotoxins which specialise in paralysis.
As of 2021, there was only one official bite documented in scientific journals. But what was revealed didn’t look good: the patient felt nothing for 6 hours, until motor issues gradually appeared, and he died at 8 hours post bite from respiratory paralysis. We don’t know much about this shy yet venomous snake, but doctors have one universal opinion: that all bites should be treated as life-threatening.
| 6 | Blue-necked keelback |
Length: 35-75cm.
Part of the same Rhabdophis genus as the red-necked keelback. The blue-necked keelback (Rhabdophis rhodomelas) lives deep in southern Thailand, as well as peninsular Malaysia over the southern border. Like the redneck version, this is a semi-aquatic snake, but tends to appear in wilder, less civilised areas, such as near swamps or deep forest streams.
The blue-necked keelback is another rear-fanged snake which chews venom in manually. Like its cousin, it was considered to be “harmless” for many years. Therefore, the question on everyone’s lips was whether the blue-necked keelback was underestimated as well, and a 2008 report hinted at a strong yes.
It happened on October 18th 2004, in Bukit Timah Nature Reserve in Singapore. At 19:40, R. Subaraj scooped up a 35cm blue-necked keelback for examination, which immediately landed a shallow bite. The keelback struggled in his grip for ten minutes, refusing to calm down, until at 19:50, it swung its jaws down hard and delivered a much deeper bite. It immediately commenced chewing, and Subaraj only dislodged it after serious effort.
Subaraj wasn’t worried, as he had previously been bitten by a paradise tree snake and oriental watersnake without event. But just 1 minute later, the world began to spin. A “cloud of darkness” engulfed him, and Subaraj fell to the floor, as his nurse wife watched and screamed.
At 19:52, Subaraj broke out in a cold sweat, and his breathing became laboured, as his wife attended to him. Emergence services arrived with a stretcher at 20:20, but Subaraj refused to go. He promised not to leave if he could walk forward in a straight line, a task he completed. His breathing was starting to improve as well.
This little researched snake seems to have extremely fast venom, both in onset and recovery. The very next day, Subaraj guided a birding client around the forest, slurring his words a little, and struggling to complete sentences, but mostly OK.
| 7 | Siamese spitting cobra |
Length: 90-120cm (max 160cm).
There are 15-20 spitting cobra species worldwide, and this is Thailand’s signature version, except for the equatorial spitting cobra which lives in the far south.
This nightmarish venom sprayer inhabits almost all of Thailand, including Bangkok and Chiang Mai, but particularly Kanchanaburi to the west. Compared to African spitting cobras, they’re less nimble with their spraying, with an average distance of 1 metre versus up to 3 metres for the black-necked spitting cobra (with 7 metres rumoured). But this snake cannot be underestimated: their aim is laser accurate, due to a well-honed recognition for the human face.
A Siamese spitting cobra facing away from you can flip around and blast your eyes in less than a second. The venom destroys eye cells, sometimes leading to permanent blindness, and its bite is equally severe. 10% of bite victims experience neurotoxic effects, beginning with drooping eyelids, double vision, and immobile eye muscles. The majority suffer from necrosis, ranging from surface skin level to deep muscle necrosis, possibly necessitating amputation.
This snake may cause 10% of bites in Thailand, as measured by dead snakes dragged into medical clinics by victims. Siamese spitting cobras (Naja siamensis) spray in a mist rather than twin jets, which brings the weather into play; being downwind could cause a bigger faceful than usual.
| 8 | Banded krait |
Length: 120-150cm (max 212.5cm).
A severely deadly snake, which is unfortunately common across most of Thailand. The banded krait (Bungarus fasciatus) appears in habitats ranging from forests to agricultural fields.
Instead of intricate, ornate patterns like a rug, Bungarus fasciatus looks like it’s been covered in a fresh lick of paint which has barely dried. It features two colours, yellow and black, in regular alternating horizontal bands. The yellow makes this species easy to identify, and that’s a good thing, because the venom’s LD50 value is 1.2mg, with a decent venom yield of 20.0 – 114.0mg. Identifying Bungarus fasciatus means that you know exactly which direction to run in.
The bite of Bungarus fasciatus is strong enough to take down large cattle within 60 minutes, and 1-10% of untreated bites are fatal in humans. A 6 year old boy was one victim, and they have a habit of crawling into people’s bedrooms at night. The usual cause of death with Bungarus fasciatus is respiratory failure, and early symptoms include abdominal pain and vomiting.
Luckily, this snake is less aggressive than the monocled cobra. National bite numbers are far lower, and a high percentage of bites are “dry”. They’re quite a lethargic snake, not fast and twitchy, at least during the day. By day, they like to hide in rodent burrows and termite mounds, or under tree stumps. Hence, we strongly recommend against sticking your arm into those places.
| 9 | Malaysian banded coral snake |
Length: 30-55cm (max 71cm).
A close relative of the better known Malaysian blue coral snake. This venomous snake mainly lives in extreme southern provinces of Thailand, adjacent to the Malaysian border.
This species has an honour bestowed upon it by nature: it’s one of 3 Calliophis species (out of 15 worldwide) to have massively elongated venom glands, which don’t just occupy their small round heads, but stretch one third of the way down their bodies, deep into their ribcage. This is one power, but the serpent gods then take away, as the Malaysian banded coral snake (Calliophis intestinalis) is hobbled by a tiny mouth.
If misfortune does strike, then this snake has some unusual symptoms rather than causing outright death. In 1937, herpetologist Edward Jacobson was bitten by a Calliophis intestinalis while helpfully brushing its dead scales away, leaving a pool of yellow venom. He instantly squeezed the wound hard, and thought he’d got away with it until 135 minutes later, when he was overcome by a severe wave of dizziness. He rushed to the telephone to ring the doctor, but was so disorientated that he could barely stand on his feet.
Over the next 6 hours, he would experience recurring waves of vomiting, perspiration and breathing struggles, but inbetween, he would be strangely OK. Likewise, his pulse was only slightly elevated. Another symptom was a dull pain at the back of his head, and 5 hours post bite he was overcome by chattering teeth and an uncontrollably shivering body. Six hours post bite, it was all over, except for some mild post-illness shakiness.
| 10 | Malaysian blue krait |
Length: 100-155cm.
A common Thai snake, whose official habitat is said to be forests, yet regularly appears in villages and even university campuses. The closely related blue krait (Bungarus candidus) has the same cause of death as the banded krait: respiratory paralysis. But this middle-sized Thai snake is even deadlier than its cousin, with a mortality rate of 60% when left untreated. The LD50 rating is 0.1mg versus 1.2mg for the banded krait, and the venom is rich in neurotoxins like candoxin.
One Thai study analysed 78 bites from Bungarus family kraits over 9 years (2008-2016). The blue krait was responsible for all 5 deaths, and most worryingly, all 5 victims received antivenin. The poison cherry on top is that bites from this species are painless, and therefore almost undetectable unless you actually see the serpent assault happen.
Are there any saving graces to this horror? Mainly that the venom yield is far lower than a banded krait at only 5mg, although 1mg can still kill a human. They’re also relaxed and lethargic a lot of the time, and don’t tend to bite people randomly walking past. Bungarus candidus is a calm and collected snake, and it takes a lot of harassment to rouse them from doziness to vicious attack mode.
Blue kraits are easy to distinguish from the safer (but still extremely dangerous) banded krait, as the stripes between the black are white rather than yellow. Blue kraits appear in every region of Thailand, except the far northwest.