| 1 | Red-headed krait |
A 150cm snake which lives in lowland rainforest, commonly less than 200 metres above sea level. By pure LD50 test, the quantity of venom required to kill 50% of animals injected into, the red-headed krait is one of the deadliest snakes on Earth.
Its venom scores 0.32mg, versus 1.2mg for a banded krait and 0.9mg for a king cobra. It’s primarily a neurotoxic venom, which causes moderate to severe paralysis. A bite from Bungarus flaviceps can freeze all muscles and connected tendons, leaving you a prisoner, hoping desperately that the doctors busying over you succeed in saving you. Fortunately, they usually do, as red-headed kraits are easily treated with antivenom. Their venom profile is similar to Thailand’s blue krait, meaning that the country’s main Bungarus antivenom works almost as well.
The cause of death from red-headed krait bite, if it happened, would be respiratory paralysis AKA lung failure. This venomous snake moves by night, and is less inclined to bite during daylight. Its red head probably evolved as a warning signal, alerting birds and great apes to its presence, proving that they have no burning desire to enter the battle fray.
| 2 | Kuri buri pitviper |
An all new venomous snake discovered in 2021, creating yet another part of Thailand that you have to tread carefully in. The Kui Buri pitviper resides in a small region of Prachuap Khiri Khan province, in central southern Thailand.
Compared to other Trimeresurus pitvipers in Thailand, they have red-purple stripes on a green background, combined with a pale green belly with very few spots, and a small white line below the eye. Its tongue is approximately the colour of a human being’s gums. Males have white spots down their spine, which females lack. The Kui Buri pitviper rests on branches most of the day, and has a gold eye with green tinges.
Every known Trimersurus pitviper member is venomous, but the exact makeup of this species toxin’ profile remains to be seen. The family tends to shred through skin tissue, but Wagler’s pitviper has unusually neurotoxic qualities. Time will tell what dark skills the Kui Buri pitviper possesses. Its 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.
| 3 | Malaysian blue coral snake |
A forest snake with venom glands stretching almost 40% down its body, which also possesses several extremely rare 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 virtually instant paralysis, sometimes within 30 seconds. It achieves this via massive stimulation of the body’s sodium channels, causing overactivation of all neurons at once.
Being so unique, calliotoxin has a unique danger – no known antidote. The Malaysian blue coral snake (Calliophis bivirgatus) mostly eats other snakes, hence why it has evolved to be one of the most rapidly paralysing snakes in the world. Two deaths are on record: 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 very docile and calm. Calliophis bivirgatus has secretive instincts, and tends to hide within leaf litter on the forest floor. Its first wall of defence is tucking its head deep within forest mulch, the second is flashing its neon red colours, and biting people comes a distant third.
| 4 | King cobra |
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. The venom is primarily neurotoxic with a side helping of skin tissue destruction, and its bite can deliver 420mg of venom.
King cobras are common in Thailand’s semi-forested areas, but also investigate agricultural areas under mankind’s control. They even slither down irrigation canals adjacent to fields, growing closer and closer menacingly. This is a snake which could hunt you down; a study from northern Thailand’s Sakaerat Biosphere Reserve found that they move 183 metres per day on average.
However, despite the terror they inspire, king cobra bites are far less common in Thailand than those from white-lipped pitvipers or monocled cobras. Another study also discovered geographical variation in the venom. This landed in Thailand’s favour, as the venom of local king cobras was less lethal than those from 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, with daily ceremonial rituals held.
| 5 | Eastern Russell’s viper |
This was formerly a subspecies of the Russell’s viper (Daboia russelli), the Indian horror which kills an estimated 20,000 people per year. 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 space. It’s mainly concentrated in central Thailand, including the outskirts of Bangkok.
Is the venom as horrifying as its western big brother? All signs suggest yes. A 2021 report involved a snake handler inspecting his charge’s mouth and nose for signs of infection, before receiving an ungrateful bite on the finger. The victim experienced throbbing pain and swelling within 30 minutes, along with neurotoxic symptoms such as numb ankles and difficulty walking.
He also experienced kidney damage, with kidney failure being the main cause of death with the main Russell’s viper. The patient was walloped with 8 vials of antivenom, including 4 within one hour, yet still showed symptoms 8 days later.
| 6 | Black-banded keelback |
This rare snake looks like a 5 year old’s first school painting project. Rhabdophis nigrocinctus belongs to the same family as the more common red-necked keelback (see our first article). Little is known 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 measures up to 100cm, and is far from a Bangkok citizen; they live in forested mountain streams, at elevations of 600-1000 metres. With such an explosion of colour in these tropical forests, they blend in better than you’d expect. They rarely encounter humans, but it wouldn’t be smart to let your hair down and start splashing around in a forest stream after having a picnic.
The black-banded keelback is an unknown quantity; it could be gentler than its red-necked cousin, but it could be far worse. They’re rare within their ranges, yet are spread across the whole of Thailand bar the far south. Black-banded keelbacks cling closely to forest and cannot cope when loggers move in.
| 7 | Guo’s green pit viper |
Another new Thai pitviper, which became an official species in 2020: Trimeresurus guoi. Guo’s pitviper resides in northern Thailand, sharing a swathe of territory with Pope’s pitviper (Trimeresurus popeiorum). The difference is that Pope’s pitviper is stiffer and more restricted to forests, vanishing when humans encroach, while Guo’s green pitviper is happy to slither around agricultural and deforested zones as well.
From a distance, they look like the same old sea of greenness, yet they have a far redder tail than most Trimeresurus pitvipers. Compared to the white-lipped pitviper (easily the most common), they have redder eyes, a friendlier face, and no sign of the signature white line.
Trimeresurus guoi is venomous, but there isn’t a single morsel of knowledge on the exact properties. They range from lowlands to 1400 metres, and often inhabit drier forests. Aside from its red tail, this is a smoothly green snake, with few intricate patterns. Guo’s pitviper averages at 50-70cm, but can reach 89cm.
| 8 | Banded sea krait |
A sea snake measuring 80-140cm, which is particularly notorious for gathering in vast numbers on the rocky shores of Phuket, Thailand’s scenic tourist city. Diving instructors are constantly informing people that while in possession of a severely neurotoxic venom, this snake has such small fangs that it’s incapable of biting through a scuba diving wetsuit.
Nai Yang Beach near Phuket International Airport is one particular hub, are the scenic Phi Phi Islands a few miles off shore. Shark Point lies inbetween, and is a gathering ground for leopard sharks, but the banded sea kraits are just as abundant. This is one of Phuket’s most poular tourist diving sights.
Staying calm and swimming right past a banded sea krait will prevent any mishaps, as they’re very docile. The LD50 rating of its venom is 0.4mg, outstripping the king cobra. Deaths that happen 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. Banded sea kraits are mostly found on the west coast of southern Thailand, being much rarer at Pattaya, for example.
| 9 | Black-headed catsnake |
A 1-1.5 metre species which occupies most of Thailand’s south, skipping Bangkok and beginning from Pattaya southwards. Most catsnakes (Boiga family) possess a weak venom spouting from their rear fangs, but Boiga nigriceps may have reached the next level. Its venom has gene transcripts for three-finger toxins, a type of neurotoxin. Boiga nigriceps apparently possesses post-synaptic neurotoxins, which block acetylcholine signals from being received in muscle cells, and is able to reduce the twitching of skeletal muscle tissue.
In the real world, this would kickstart the chain of events that leads to paralysis. The neurotoxins’ potency was comparable to the Australian tiger snake’s. Black-headed catsnakes are one of the worst of their family, but they still have to position their head awkwardly to pierce their rear fangs through your skin. They’re reluctant to bite full stop, normally beginning with a series of mock lunges rather than going straight for death dealership.
The black-headed catsnake dwells in forests, sticking close to water sources within, often dangling down from a branch to search for frogs.
| 10 | Small-spotted coral snake |
The small-spotted coral snake (Calliophis maculiceps) lives all over Thailand, often appearing in gardens curled up in potted plants or within leaf litter. It belongs to the same family as the Malaysian blue coral snake, but without the freaky torrent of venom. The Calliophis family is divided into long-glanded and short-glanded snakes, and this species belongs to the latter. However, its 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 Calliophis maculiceps at the Sakaerat Environmental Research Station in northeast Thailand. The snake was slithering around on the bathroom tiles, and within the hour, his 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 had 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 50cm (the species’ maximum) could inject more venom and more danger.