Bitten by a Venomous Snake in Thailand? — What Happens, Hour by Hour

If you have just been bitten by a venomous snake in Thailand, you have one of the better outcomes available globally for snakebite. Thai hospitals are well-stocked with antivenom, the protocols are good, and outcomes for patients who reach a hospital within an hour or two of the bite are excellent. This piece is the hour-by-hour timeline of what happens — from the moment of the bite to discharge from hospital — for the three main bite types you might encounter: viper, cobra, and krait.

Minute zero — the bite

The bite itself is usually surprisingly underwhelming. Two small punctures, sometimes only one. A sharp pain like a bee sting. The realisation usually comes a beat or two later. Two clear fang marks 1–2 cm apart suggest a viper or cobra; harder-to-see, smaller marks may be a krait, often under 1 cm apart.

What to do: see our snakebite first-aid guide. Briefly: get away from the snake, sit down, immobilise the limb, remove rings and watches, photograph the snake from 2 m if safe, and start moving toward a hospital.

Minutes 1 to 30 — the early window

For viper bites: pain at the bite site usually intensifies. Mild swelling starts. The bite area may begin to bruise. Some patients report a metallic taste. For cobra bites: the local effects start more slowly, but neurological signs may begin — drooping eyelids (ptosis), slight slurring of speech, drowsiness. For krait bites: usually nothing at all in this window. Krait bites have a famously slow onset and people sometimes go to bed feeling fine after a midnight bite.

This is the critical transit window. Get to a hospital, or get the patient to a hospital. Thai provincial hospitals all stock the basic antivenoms.

Hours 1 to 6 — at the hospital

Triage, history, examination of the bite. The 20-Minute Whole Blood Clotting Test (20WBCT) goes in: 2 mL of blood in a clean glass tube, watched for 20 minutes; failure to clot indicates a coagulopathy and is the bedside indicator for viper envenomation. Vital signs monitored continuously. Neurological examination repeated every 15–30 minutes for cobra/krait bites.

Antivenom: if envenomation is confirmed, antivenom is given intravenously, usually 5–10 vials (the dose depends on species and clinical severity). Monitoring for anaphylactic reaction during infusion. The Thai polyvalent antivenoms cover all the medically important species.

Hours 6 to 24 — observation

For viper bites: pain and swelling continue to increase. The limb may become tense and shiny. The 20WBCT is repeated; if it remains uncoagulable, more antivenom is given. Some patients need fasciotomy (surgical decompression) if compartment syndrome develops. For cobra bites: respiratory function watched closely. Patients with progressing paralysis are intubated and ventilated. Antivenom and supportive care continue. For krait bites: paralysis often peaks here. Ventilation may be needed for several days.

For Red-Necked Keelback bites — even ones that “looked fine” — coagulopathy may develop in this window. See our delayed-coagulopathy notes for the full picture.

Day 2 to 7 — recovery

Most patients improve substantially by day 2 with appropriate treatment. Viper bites continue to swell and may cause prolonged disability for weeks. Cobra and krait patients ventilated through the acute phase usually recover full neurological function. Tissue damage at the bite site for cobra and viper bites can require ongoing wound care.

Discharge typically happens after 3–7 days for uncomplicated viper bites, longer for cobras and kraits requiring ventilation. Long-term follow-up watches for any residual neurological deficit, kidney function (especially after sea-snake or Russell’s Viper bites), and wound healing.

What this means in practice

Thai snakebite outcomes for patients who reach a hospital within 1–2 hours of the bite are excellent. Mortality with antivenom and supportive care is below 1% for the major Thai species. The single biggest predictor of bad outcome is delay — patients who wait at home for hours or try folk remedies do far worse than patients who go straight to hospital.

For the practical day-to-day prevention picture see avoiding snakebites in Thailand. For the species-by-species threat picture see common venomous Thailand snakes.

External references: the WHO snakebite envenoming hub for international treatment guidelines and the Queen Saovabha Memorial Institute, the central Thai antivenom production and reference centre.

Key takeaways

• Context matters more than rules of thumb. Thailand’s snake fauna varies meaningfully by region, by season, and by habitat. Advice that holds in southern wet forest does not always hold in northern hill country or in the central agricultural plains.
• Prevention is high-leverage. Most serious snake-related incidents in Thailand are downstream of three preventable behaviours — reaching where you cannot see, walking forest paths at night without a torch, and attempting to handle or kill snakes rather than call professional removal.
• Hospital access is the real safety net. Thai provincial hospitals stock the standard polyvalent antivenoms. The single biggest predictor of bad outcome from a serious bite is delay in reaching one of those hospitals.
• Citizen-science records help. Even casual photographs with location data, posted to platforms like iNaturalist, contribute to the regional knowledge base. Most Thai snake species have surprisingly thin distribution data; one well-documented sighting can fill a real gap.

Common questions

How likely am I to see a snake on a casual visit to Thailand?

Lower than you probably expect. A casual three-hour daytime forest hike in southern Thailand has roughly a 5–10% chance of producing any snake encounter at all, and roughly a 0.5–1% chance of producing a venomous-species sighting. Visitors who deliberately go looking — at night, in good habitat — see far more, but the casual exposure is genuinely low.

What time of year has the most snake activity?

The wet season (May through October) produces by far the most snake encounters across most of Thailand. Within that, two peaks: the start of the rains (April–June) when males are moving for breeding, and late wet season (September–November) when juvenile cohorts disperse from nest sites. The dry season (December–March) is genuinely quieter for snake-watching, particularly in the north and northeast.

Are Thai snakebite outcomes really that good?

For patients who reach a hospital within an hour or two of a venomous bite, yes — Thai outcomes are excellent by international standards. Mortality with appropriate antivenom and supportive care runs under 1% for most species. The deaths that do happen are concentrated in cases of significant pre-hospital delay, mis-identification of species, or in patients with serious co-morbidities. The Thai system is robust; the failure modes are mostly upstream of the hospital.

What is the single best preventive measure?

A torch at night. The single biggest reducer of Thai snakebite risk is consistent, eyes-down torch use on every walking path after dark. Most preventable bites in southern Thailand are foot-on-snake events on the ground at night, and a torch beam on the trail at metre-down angle prevents the great majority of them. Closed footwear is the second-biggest improvement; long trousers in dense vegetation is third.