| 1 | Red-headed krait |
Maximum length: 207cm.
A nocturnal snake which rarely appears in towns and villages, sticking mainly to lowland rainforests. Red-headed kraits (Bungarus flaviceps) aren’t found near Bangkok, but are abundant in the southern regions of Thailand, as well as Malaysia and Sumatra.
Instead of hilly forests, this species prefers lower areas, usually from 0 to 900 metres in elevation, with an absolute record of 1200 metres. As measured by the LD50 scale, this species has one of the most toxic snake venoms on Earth. The LD50 score is 0.32mg, which easily outstrips their cousin the banded krait (1.2mg), and even a king cobra (0.9mg).
The venom of this species is primarily neurotoxic, causing moderate to severe paralysis. A bite from a red-headed krait can freeze all muscles and connected tendons, leaving you a prisoner, hoping desperately that the doctors busying over you succeed in saving your life.
Fortunately, they usually do, as Bungarus flaviceps bites are easily treated with antivenom. Their venom profile is similar to Thailand’s blue krait (Bungarus candidus), meaning that the country’s main Bungarus krait antivenom works almost as well. The cause of death, if it did occur, would be respiratory paralysis, as the commanding signals from the brain to lungs completely shut down. Red-headed kraits are mostly nocturnal, and are less inclined to bite during daylight.
| 2 | Kuri buri pitviper |
Maximum length: 52.2cm (so far).
An all-new venomous snake discovered in 2021, creating yet another part of Thailand which you have to tread carefully in. The Kui Buri pitviper (Trimeresurus kuiburi) resides in a small region of Prachuap Khiri Khan province, in central southern Thailand. Its discovery brought the total number of Trimeresurus pitvipers in Thailand to 14, which has since grown to 18 as of December 2024.
Compared to other members in Thailand, Kui Buri pitvipers are recognisable by red-purple stripes on a green background. They have a pale green belly with very few spots, and a small white line below each eye. Their tongue is approximately the colour of a human being’s gums. Males have white spots down their spine, which females completely lack.
The Kui Buri pitviper is a fairly small snake, which rests on branches for the vast majority of the day. Being so new, we don’t have an all-time length record yet, but in the initial study, the snakes the scientists collected measured 37-52cm.
All Trimeresurus pitvipers are dangerously venomous, but the exact toxin profile of this species remains to be seen. The group tends to shred through skin tissue, rather than be neurotoxic like a coral snake. The Kui Buri pitviper’s closest relative was found to be the large-eyed pitviper (Trimersurus macrops), whose venom causes mass necrosis and has a half life in the body of 14 days. Only time will tell what dark skills the Kui Buri pitviper possesses.
| 3 | Malaysian blue coral snake |
Maximum length: 185cm.
An extremely dangerous snake, which you could probably survive walking past, but would be virtually guaranteed to die from if you touched. The Malaysian blue coral snake (Calliophis bivirgatus) is found across a large swathe of southern Thailand, as well as Malaysia and Indonesia. This species has incredibly long venom glands, stretching almost 40% of the way down its body, and its venom has several unique toxins.
The first is maticotoxin, making up 30% of the venom, a cytotoxin which ruptures the membranes and walls of skin cells. The second is the most potent – calliotoxin, which causes almost instant paralysis, sometimes within 30 seconds. It achieves this via massive stimulation of the body’s sodium channels, causing overactivation of all neurons simultaneously.
Being so unique, calliotoxin has a unique danger – no known antidote. The Malaysian blue coral snake mainly feeds on other snakes, which is a dangerous menu. Hence, it has evolved to have one of the most rapidly paralysing venoms in the world.
Two deaths are on record for Calliophis bivirgatus: a Malaysian child who died within 2 hours in 1956, and a showering Singapore man who died within 5 minutes after being bitten on the toe. Fortunately, this snake is relatively docile and calm. Blue coral snakes mainly live in forests, and have secretive instincts, preferring to hide within leaf litter on the forest floor, rather than launch all-out assaults on humans.
| 4 | King cobra |
Maximum length: 5.85 metres.
One of the world’s most notorious snakes, the king cobra occupies virtually all of Thailand. There’s barely an inch of the country where they can’t rear their ugly head. Their venom is primarily neurotoxic, with a side helping of skin tissue destruction, and their bite can deliver 420mg of venom in seconds. At a confirmed wild record of 5.85 metres, this is the longest venomous snake on Earth, ahead of the black mamba in 2nd place.
King cobras are rarely found in urban areas. They’re most common in Thailand’s forested and semi-forested regions, but also appear in agricultural areas under mankind’s control. They can even slither down irrigation canals directly adjacent to fields, and often stash themselves in hollows in tree trunks.
This is a snake which could hunt you down, as a study from northern Thailand’s Sakaerat Biosphere Reserve found that king cobras move 183 metres in an average day. However, despite the terror they inspire, king cobras bite significantly fewer people in Thailand than the smaller monocled cobra or Siamese spitting cobra (see our first article).
Another study discovered geographical variation in the venom. This landed in Thailand’s favour, as the venom of the local king cobras was less lethal compared to those in China and Indonesia. Thai king cobra bites were also easier to treat with antivenom. There’s even a king cobra village in Thailand called Ban Khok Sa-nga, where they’re kept as pets, and honoured with daily ceremonial rituals.
| 5 | Eastern Russell’s viper |
Maximum length: 127cm.
This was formerly a subspecies of the Russell’s viper (Daboia russelli), the Indian horror which kills an estimated 20,000 people per year (possibly the most of any snake). In 2007, the Burmese and Thai versions were separated into their own species: Daboia siamensis.
The eastern Russell’s viper averages at 100cm, and differs in appearance by having smaller dark spots between the large blotches, rather than empty spaces. It’s mainly concentrated in central Thailand, including the outskirts of Bangkok. Daboia siamensis is smaller than its Indian cousin, and currently has an all-time record of 127cm.
Is the venom as horrifying as its western big brother? All signs suggest yes. In a 2021 report, a snake handler was inspecting the mouth and nose of an eastern Russell’s viper for signs of infection, when he received an ungrateful bite to the finger. The victim developed throbbing pain and swelling within 30 minutes, along with neurotoxic symptoms such as numb ankles and difficulty walking.
He also experienced kidney damage, which was telling, as kidney failure is the main cause of death with the Indian Russell’s viper. Clearly, the two have a fairly similar venom. The patient was walloped with 8 vials of antivenom, including 4 vials within one hour, yet still showed symptoms 8 days later.
| 6 | Black-banded keelback |
Maximum length: 95cm.
This rare Thai snake looks like a 5 year old’s first painting project at school. The black-banded keelback (Rhabdophis nigrocinctus) belongs to the same genus as the more common red-necked keelback (see our first article). Little is known about their personality, except that their saliva contains a potent venom. If they’re anything like their cousin, they’ll hold onto their victims and chew repeatedly to force the venom in.
Rhabdophis nigrocinctus is a widespread species, but far from a Bangkok citizen. They’re found in most regions of Thailand, but only near mountain streams within deep forests, at elevations of 600-1000 metres.
With such an explosion of colour in these tropical forests, the black-banded keelback blends in effortlessly. It’s rare for humans to encounter this venomous snake, but it still wouldn’t be smart to let your hair down after a picnic and start splashing around in a random forest stream, or a scenic Thai lagoon.
The black-banded keelback is an unknown quantity; it could be gentler than its red-necked keelback cousin, or it could be far worse. They’re rare within their territory, yet are spread across the whole of Thailand, bar the far south. Black-banded keelbacks cling closely to forests, and cannot cope when loggers move in.
| 7 | Guo’s green pit viper |
Maximum length: 89cm.
Another newly discovered Thai pitviper, which only became an official species in 2020. Guo’s green pitviper (Trimeresurus guoi) resides in northern Thailand, sharing a swathe of territory with Pope’s pitviper (Trimeresurus popeiorum). The two differ significantly in habitat, as Pope’s pitviper is significantly less flexible, restricting itself to forests and vanishing when humans encroach. Meanwhile, the new Guo’s pitviper was happy to slither around agricultural and deforested areas as well.
From a distance, Guo’s pitviper looks like the same old sea of greenness, yet they have a far redder tail than most Trimeresurus pitvipers. Compared to white-lipped pitvipers (easily the most common member), they have redder eyes, and the namesake white line is less obvious.
Guo’s green pitvipers are venomous, but there isn’t a single morsel of knowledge on the exact properties. They range from lowlands to 1400 metres above sea level, and often inhabit drier forests. Aside from its red tail, this is a smoothly green snake, with few intricate patterns. Guo’s green pitvipers average at 50-70cm, but the largest so far reached 89cm.
| 8 | Banded sea krait |
Maximum length: 152.5cm.
A severely neurotoxic sea snake, which averages at 80-140cm. This species is notorious for gathering in vast numbers along the rocky shores off Phuket, Thailand’s scenic tourist city. Take a scuba diving excursion in Phuket, and you’re almost guaranteed to see them, but luckily, this snake has such small fangs that it’s incapable of biting through a standard black wetsuit.
The banded sea krait (Laticauda colubrina) has an LD50 toxicity rating of 0.4mg, which beats a king cobra. Nai Yang Beach near Phuket International Airport is a particular hub for them, as are the scenic Phi Phi Islands a few miles off shore. Shark Point lies inbetween, and is an infamous gathering zone for leopard sharks, but the banded sea kraits here are just as abundant. This is one of Phuket’s most popular tourist diving sights.
Staying calm and swimming right past a banded sea krait will prevent most mishaps, as they’re very docile. Deaths that do occur are usually due to fishing trawlers scooping them up in nets by accident, emptying the contents, and suffering a nasty shock as a snake latches onto their finger.
Within Thailand, banded sea kraits are mostly found along the southwest coast. For example, they’re far rarer near Pattaya further east.
| 9 | Black-headed catsnake |
Maximum length: 200cm.
A 100-150cm species which occupies most of Thailand’s south, skipping Bangkok and Pattaya, but appearing across all areas of the thin southern peninsular. The black-headed catsnake (Boiga nigriceps) dwells in forests, sticking close to water sources within. They’re often seen dangling down from a thin tree branch, searching for frogs.
Most catsnakes (Boiga genus) possess a weak venom injected by their rear fangs, but the black-headed catsnake (Boiga nigriceps) may have reached the next level. Like a black mamba (albeit much weaker), its venom has gene transcripts for three-finger toxins, a type of neurotoxin. Boiga nigriceps apparently possesses post-synaptic neurotoxins, which prevent acetylcholine brain signals from being received in muscle cells. In lab experiments, these were able to reduce the twitching of skeletal muscle tissue.
In the real world, this would kickstart the chain of events that leads to paralysis. According to a 2004 study, the potency of Boiga nigriceps’ neurotoxins was comparable to those of the Australian tiger snake.
Consequently, black-headed catsnakes are one of the more dangerous Boiga catsnake members, but they still have to position their head awkwardly to pierce their rear fangs through skin. They’re reluctant to bite full stop, normally beginning with a series of mock lunges rather than going straight for the kill.
| 10 | Small-spotted coral snake |
Maximum length: 50cm.
A shy, poorly researched, yet potentially lethal Thai snake. The small-spotted coral snake (Calliophis maculiceps) lives in all regions of Thailand, often appearing in gardens curled up in potted plants, or hidden within layers of leaf litter. It belongs to the same Calliophis genus as the Malaysian blue coral snake, but is far smaller, at a maximum of just 50cm. It also lacks the freakish torrent of venom, and the notoriously long venom glands covering 40% of its body.
The Calliophis genus is divided into long-glanded and short-glanded snakes, and this species belongs to the latter. However, it’s still capable of causing body-wide symptoms.
Bites are rare, and the first proper report ever happened on October 11th 2017, when a scientist was bitten on the right index finger after picking up a small-spotted coral snake at the Sakaerat Environmental Research Station in northeast Thailand. The snake was slithering around on some bathroom tiles, and within the hour, the scientist’s finger was swollen and throbbing. Soon, a strange numbness appeared in his chin and cheeks.
By 3 hours post bite, his arm and elbow were also aching painfully. The man developed an uncomfortable feeling in his throat, which made it difficult to swallow. Most unusually, a hardened callus appeared around the fang marks over two weeks after the bite. This snake was a juvenile measuring just 20cm, so an adult measuring 40cm could inject more venom, and much more deadliness.
Small-spotted coral snakes are poorly researched, with many blind spots remaining in scientists’ logbooks. Their diet is theorised consist of tiny snakes such as blind snakes.