Thailand's general drink-driving limit is 50 milligrams of alcohol per 100 millilitres of blood — written locally as 50 mg%, and the same thing as 0.05% BAC. A second, far lower limit of 20 mg% (0.02% BAC) applies to a defined group of drivers, and a great many visitors are in that group without knowing it.
The number is the easy part. Three things matter more. The lower limit catches anyone driving a vehicle their licence does not cover, which describes most tourists on a rented scooter. Refusing the breath test does not get you out of it, because Thai law then presumes you were over. And a positive test does not produce a roadside ticket — it produces a court file.
- General limit50 mg% (0.05% BAC)
- Lower limit20 mg% (0.02% BAC)
- Lower limit applies toUnder-20s, provisional licences, wrong-category and unlicensed drivers
- Primary testRoadside breath test
- Not a ticket offenceGoes to the inquiry officer and the court
The two limits, and which one is yours
Both limits come from a ministerial regulation on testing the alcohol content of drivers, signed by the Prime Minister on 3 September 2024 and published in the Royal Gazette on 20 September 2024. It replaced the earlier regulations from 1994 and 2017, and it is the instrument that put the two-tier structure in place.
The 50 mg% limit is the default. It applies to an adult driving a vehicle they are properly licensed for. The 20 mg% limit — effectively a zero-tolerance rule, because a single drink can carry an ordinary adult past it — applies to four categories of driver:
- Drivers under 20 years old.
- Holders of a provisional or temporary driving licence.
- Drivers holding a licence for a different category of vehicle from the one they are actually driving.
- Drivers with no licence at all, or whose licence is suspended or revoked.
Read the third one again, because it is the one that reaches into a normal two-week holiday. A visitor who holds a car licence at home, rents a 125cc scooter in Phuket and rides it with no motorcycle entitlement and no motorcycle category on their international driving permit is driving a category their licence does not cover. Their limit is 20 mg%, not 50 mg%, regardless of their age and regardless of the fact that nobody stopped them on the way to the restaurant. If you are not certain which side of that line you are on, which licence you can use in Thailand works through it properly.
What the law says
Section 43(2) of the Land Traffic Act B.E. 2522 (1979) prohibits driving "while got drunk of alcohol or other intoxicant" — the wording of the Royal Thai Police's own English translation. The Act itself sets no number. The numbers live in the 2024 ministerial regulation, which also lays down how the test is to be carried out.
What 0.05% actually means at a Thai dinner table
We do not publish a chart of drinks against blood-alcohol readings, and we do not have a calculator. That is a deliberate editorial decision rather than an oversight. Every such tool works by producing an estimate, and the only use anyone ever makes of the estimate is to decide they are probably just under. The error bars on those calculations are wide enough — between individuals, between the same person on different days, and between the calculation and an actual breathalyser — that acting on one is a genuinely dangerous thing to do.
What we can usefully say is which local factors push in the wrong direction.
The measures are bigger than they look. Beer arrives in the large bottle unless you ask otherwise, and the default is closer to two drinks than one. Spirits poured at a beach bar are not measured. The bucket sold on the islands has no defined contents at all.
Heat and dehydration change how you feel, not how you test. A long hot day, sweating, not eating much: you will feel the first drink more, and you may also feel sober again sooner than the alcohol has actually cleared. The breathalyser reads the alcohol, not the feeling.
Clearance is slow and cannot be hurried. Coffee, a shower, food and a swim change nothing measurable. Alcohol leaves the body at its own pace, and a heavy night genuinely can leave a rider over the limit at breakfast — which is when a great many people get on a scooter to ride back to their hotel.
The morning ride is the underrated one. Checkpoints run at night, but the risk you carry the next morning is not the ticket — it is that you are riding an unfamiliar machine on Thailand's roads with impaired reaction time, in traffic that requires you to read other people's intentions constantly. If last night was heavy, take a taxi and collect the bike later. Nobody at the rental shop will mind.
How the test is done
The breath test is the primary method, and it is what you will meet at a roadside checkpoint: a handheld unit, a disposable tube, one breath. It is quick, and if you are clear you are waved on within a minute or two.
The 2024 regulation also provides for two alternatives where a breath test cannot be carried out — after a crash, for example, or where the driver is injured or physically unable to blow. A urine sample must be taken into a sealed container in a private collection area and analysed by a laboratory. A blood sample must be taken by medical staff at a hospital. Neither is a roadside procedure and neither is something an officer can do informally.
If you have been in a collision and are taken to hospital, expect alcohol testing to form part of what happens there. That sequence is dealt with in what to do after a road accident in Thailand, which is worth reading before you need it rather than after.
Refusing the test makes it worse, not better
This is the single most important legal fact on the page, and the one visitors most often have backwards. Under section 142 of the Act, where there is reasonable ground to believe a driver is intoxicated and the driver refuses a test without reasonable justification, it is presumed that they have breached section 43(2). Not an adverse inference that a court may draw — a presumption written into the statute.
The officer may also detain a driver who refuses, for as long as is reasonably necessary to complete the test. If the driver then agrees and tests negative, they must be released without delay. The Royal Thai Police confirmed the position publicly in 2026: refusal is treated as equivalent to drink-driving and attracts the same penalties. Separately, disobeying an officer's lawful order to stop or to submit to a test is itself an offence carrying a fine of up to 1,000 baht each time.
There is no Thai equivalent of the British "failure to provide" as a lesser charge you might prefer to a positive reading. Refusing a breath test in Thailand sets out exactly what follows.
What happens after a positive test
Drink-driving is not a fixed-penalty matter. Section 140 of the Act expressly excludes the drink-driving and drug-driving offences from the warning-and-ticket process, which means an officer cannot deal with it at the roadside at all. The case goes to an inquiry officer and then to court. In practice that means the vehicle is stopped where it is, you are taken to a police station, and you are dealt with over hours rather than minutes.
| Outcome | Penalty range in the Act | Licence |
|---|---|---|
| First offence, no harm caused | Up to 1 year and/or 5,000–20,000 baht | Court must suspend for at least 6 months, or revoke |
| Causing injury | 1–5 years and 20,000–100,000 baht | Suspended at least 1 year, or revoked |
| Causing serious injury | 2–6 years and 40,000–120,000 baht | Suspended at least 2 years, or revoked |
| Causing death | 3–10 years and 60,000–200,000 baht | Revocation is mandatory |
A repeat offence within two years carries up to 2 years and/or 50,000–100,000 baht. Twenty thousand baht is roughly £450, $600 or €520; the upper figures in that table are life-altering sums. The full picture, including what the licence suspension means for someone who does not hold a Thai licence, is in drink-driving penalties in Thailand. For residents, drink-driving also sits in the top band of Thailand's licence points system at four points from a starting balance of twelve.
The consequence that arrives first: your insurance
Long before a court date, a positive test or a refusal does something more immediate. Alcohol is a universal exclusion in travel insurance and in motor cover, and an insurer does not need a conviction to decline — it needs a police report, a hospital note or a positive reading on file.
That matters more in Thailand than almost anywhere, because of what the compulsory motor insurance actually covers. Por Ror Bor attaches to the vehicle, pays for injury rather than damage, and is capped at levels a private hospital in Bangkok or Phuket can pass in a day. It is a floor, not a safety net. Everything above it depends on cover that alcohol switches off. What voids your motorbike cover in Thailand is the page to read on this, and medical evacuation insurance explains the bill that follows when the cover has gone.
The pillion passenger is exposed too. Travel policies commonly condition motorcycle cover on the licence held by whoever is in control of the machine. A passenger who has drunk nothing can find their own claim contested because of who was riding. If you are travelling as a pair, that is worth knowing before you decide who takes the keys.
Where you will actually meet a breath test
Checkpoints are routine at night on the approach roads to nightlife districts and beaches, and at provincial boundaries. They are not hidden; you will see the cones and the lights well before you reach them. Drink-driving is also on the Royal Thai Police's list of ten offences singled out for strict enforcement from April 2026, alongside speeding, helmets and seatbelts.
Two periods change the picture completely: the "seven dangerous days" around Songkran in April and the equivalent stretch over New Year, when breath-testing is set up on main roads across the country. Drink-drive checkpoints at Songkran and New Year covers what to expect and how to plan around it. If you want the general shape of a Thai traffic stop first, police checkpoints in Thailand describes the routine one.
The alternatives are unusually good
Thailand is one of the easier countries in the world in which not to drive after a drink. Grab operates in every city and most tourist towns and will bring a car or a motorbike taxi to a bar at two in the morning. Motorbike taxis wait at the mouth of almost every soi. Songthaews run fixed routes in Chiang Mai, Pattaya and the islands until late. A rented scooter left chained outside a bar overnight is a normal sight and costs nothing but the walk back to collect it in the morning.
The decision to make in advance is the boring one: agree before you go out how you are getting home, and put the bike keys somewhere that requires a decision to retrieve them.
Frequently asked questions
Is the drink-drive limit different for motorbikes?
Not in itself. The 50 mg% and 20 mg% limits are set by the driver's situation, not by the vehicle. But the effect is that most tourists on a scooter are on the lower limit anyway, because they are riding a category their home licence does not cover.
Does an international driving permit change which limit applies to me?
It can, because the question is whether you hold a valid entitlement for the vehicle you are driving. An IDP that carries the motorcycle category, issued on the back of a home licence that carries it, is what puts a rider on the general 50 mg% limit rather than the lower one. An IDP with only the car category does not.
Can I be tested if I have already parked and got off the bike?
The officer's power to require a test under section 142 arises in relation to a driver, and in practice testing happens at the roadside when a vehicle is stopped. If you have been in a collision, testing can follow at the hospital or the station regardless of where the vehicle ended up.
What if I am the passenger and the rider has been drinking?
You commit no traffic offence, but you carry the risk. Your travel policy may treat the rider's condition and licence as conditions of your own cover, and in a crash the person on the back is more exposed than the person in front.
Do the police accept a fine at the roadside for drink-driving?
No. The Act removes drink-driving from the fixed-penalty process entirely, so there is no lawful amount to pay at the roadside and no ticket to be issued. If money is discussed at the scene, nothing is being settled. What travellers report about informal roadside payments covers that ground; what a legitimate receipt looks like covers the other half.
Does the limit apply to cyclists?
The Act applies a large part of the driving rules to cyclists through section 84, and the prohibition on driving while intoxicated sits in the general driving provisions. Treat riding a bicycle after drinking as covered, and treat it as a bad idea in Thai traffic in any case.
Will a drink-driving conviction affect my visa or future entry?
That is an immigration question rather than a traffic one and we do not have a source we would rely on. What we can say is that a case that goes to court is a criminal matter, not an administrative fine, and that anyone facing one should get proper legal advice in Thailand rather than relying on a website. Your embassy's consular section can supply a list of local lawyers, and the tourist police on 1155 can get you an English-speaking officer in the meantime.