| 1 | Monocled cobra |
Length: 1.35-1.5m.
The snake responsible for the most deaths in Thailand. Monocled cobras have an LD50 venom toxicity score of 0.23-0.37mg, and a high venom yield of 263mg compounds the danger. Monocled cobras wrap up all the dangers into one savage package, as they have an aggressive temperament, and they commonly occur around human habitation.
This species will battle its way into a kitchen while a man brandishes a broomstick, pop out from under a fridge to bite you on the toe, and reappear in your well-manicured garden no matter how many reptile controllers remove them. Every Thai resident is said to have a monocled cobra story, or a friend or relative assaulted by one. Monocled cobras inhabit the majority of Thailand, including bustling Bangkok, but are centred around the middle, skipping the far south and northeast.
The venom causes both massive skin necrosis and neurotoxicity, via the compound alpha-cobratoxin. Do not mess with the monocled cobra. Remember that time is key – get yourself or loved one to hospital as fast as possible.
| 2 | Red-necked keelback |
Length: 60-80cm.
A common snake across Thailand, often found in long grass near ponds. The red-necked keelback’s claim to fame is that everyone once thought it was harmless. People kept them as low-maintenance household pets, feeding and touching them happily. Red-necked keelbacks lack front fang venom, instead secreting venom from their rear fangs which flows into bite wounds, through tiny canal-like grooves. The snake has to chew repeatedly, so people assumed that to cause harm, you’d have to leave the snake attached for 2 minutes.
But slowly, reports of life-threatening hospitalisations emerged. A child was chewed for just two seconds, and a man was chewed for 20 seconds, sending both to intensive care for a week. The venom potency was tested and proven to be 1.29mg, not earth-shattering, but with the potential to cause brain haemorrhages and kidney failure.
Being such recent developments, the red-necked keelback lacks a dedicated antivenin. They add to the danger with poison stored in their signature red-neck, acquired from toads they ate, ready to burst if you touch them. Thai Villagers once walked past this snake with no worries. Unfortunately, many still do, as news is slow to trickle out.
| 3 | White-lipped pit viper |
Length: 60-80cm.
The green pitviper family is a level below the monocled cobra. They all have venom, and while it isn’t automatically deadly, it wreaks havoc on the human body and virtually guarantees a hospital visit. The white-lipped pit viper is especially notorious, being common across most of Thailand. It’s nearly entirely green, except that for the signature white-lip, which extends all the day down their body, outlining the pale green belly.
The venom specialises in haemorrhages, with possible tissue necrosis in severe bites. The potency matches the monocled cobra, at LD50 0.37mg, but the venom yield is much lower at 8-15mg. This is why it kills people less, but occasional deaths have been reported. This brightly coloured venomous snake has a particular tendency to pop up in gardens, including inside Bangkok itself. They can be very common locally; some have found dozens in an hour. A top situation for being bitten is doing garden work, maybe bending over and absentmindely whistling a tune.
Luckily, Thai hospitals are well prepared, as they nearly always stock the generic green pit viper venom (useful for all species).
| 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. Trimeresurus venustus is covered with alternating red and green patterns to create an exotic tapestry of colours, along with supreme camouflage. You won’t find this snake in Bangkok, as it lives 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.
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 his beautiful pit viper from a feeding box. The finger became painful and swollen, and within an hour this had spread to the rest of the 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. It 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 stands apart as only member of the Sinomicrurus family. MacLelland’s coral snake is active at night, and hunts slowly and deliberately, shifting patiently through leaf litter. 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 it seems to have been stepped on.
MacLelland’s coral snake 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, Sinomicrurus macclellandi 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 solid opinion: all bites should be treated as life-threatening. Sinomicrurus macclellandi inhabits the central and northwestern areas of Thailand.
| 6 | Blue-necked keelback |
Length: 35-75cm.
Part of the same Rhabdophis family as the red-necked keelback. It’s another rear-fanged snake which chews venom in manually, and it was also considered “harmless” for years. The question on everyone’s lips was whether the blue-necked keelback was underestimated as well. 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. It struggled in his grip for ten minutes, refusing to calm down, until at 19:50, it swung its jaw down and landed a deep bite. It immediately commenced chewing, and Subaraj only dislodged it after serious effort. He wasn’t worried, as he had been bitten by a paradise tree snake and oriental watersnake before without event. But just 1 minute later, everything started 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 him. Emergency services arrived with a stretcher at 20:20, but Subaraj refused to go. He promised not to go 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 next day, Subaraj guided a birding client around the forest, slurring his words a little and struggling to complete sentences, but mostly okay.
The blue-necked keelback lives deep in southern Thailand, so Bangkok-ers need not fear. Like the redneck, it’s a semi-aquatic snake that hangs out in swamps and forest streams.
| 7 | Siamese spitting cobra |
Length: 90-120cm.
There are 15 spitting cobra species, and this is the Thailand version, except for the equatorial spitting cobra which lives in the far south. This 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 (7 metres rumoured). But this snake can’t be underestimated: their aim is laser accurate, due to a well-honed recognition for the human face.
A Naja siamensis facing away from you can flip around and blast your eyes in less than a second. The venom destroys eye cells and can cause permanent blindness. The bite is equally severe. 10% of victims suffer from neurotoxic effects, beginning with drooping eyelids, double vision, and immobile eye muscles. The majority suffer from necrosis, ranging from surface skin level to deep muscles, possibly causing amputation.
This snake may cause 10% of bites in Thailand, as measured by dead snakes dragged into the clinic later by victim. Siamese spitting cobras spray in a mist rather than twin jets, which brings the weather into play; being downwind could cause a faceful.
| 8 | Banded krait |
Length: 1-1.5 metres.
A common snake over most of Thailand, 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 stripes. The yellow makes it easy to identify, and that’s a good thing, because the venom’s LD50 value is 1.2mg, with a strong venom yield of 20.0 – 114.0mg.
Its bite is strong enough to take down large cattle within 60 minutes, and 1-10% of untreated bites are fatal. A 6 year old boy was one victim, and they have a habit of crawling into people’s bedrooms. The cause of death with this snake is usually 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. By day, they like to hide in rodent burrows and termite mounds, or under tree stumps. That said, it’s probably not wise to stick your arm into these dark places.
| 9 | Malaysian banded coral snake |
Length: 30-55cm.
A close relative of the better known Malaysian blue coral snake. This venomous snake mainly lives in southern provinces adjacent to the Malaysian border. It has an honour bestowed upon it by nature: it’s one of 3 calliophis species to have massively elongated venom glands, which don’t just occupy their small round heads, but stretch 1 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 outright death. In 1937, herpetologist Edward Jacobson was bitten while helpfully brushing 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 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 post-illness shakiness.
| 10 | Malaysian blue krait |
Length: max 1.6 metres.
The closely related blue krait (bungarus candidus) has the same cause of death as the banded krait: respiratory paralysis. But this common Thai snake is far deadlier, with a mortality rate of 60% if left untreated. The LD50 rating is 0.1mg versus 1.2mg, rich in neurotoxins like candoxin. They materialise in villages, towns or even university campuses.
One Thai study logged 78 snake bite victims over 9 years, from multiple species. The blue krait was responsible for all deaths, and most worryingly, all victims received antivenin. The poison cherry on top is that bites from this species are painless, and almost undetectable.
Are there any saving graces to this horror? Mainly that the venom yield is far lower at only 5mg, although 1mg can kill a human. They’re also relaxed and lethargic a lot of the time, and don’t tend to bite people randomly walking past. They’re 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 dangerous) banded krait, as the stripes between the black are white rather than yellow.