Motorbikes, Filtering and Thailand's Left Lane

Thai law puts motorcycles in the leftmost lane. Section 35 of the Land Traffic Act requires motorcycles, trucks and passenger-transport vehicles on any road with two or more lanes in the same direction to use the leftmost lane, or the lane immediately next to a bus lane. Private cars and small private goods vehicles up to 1,600 kg are expressly exempted from that rule; motorbikes are not.

It is also the most consistently ignored rule in the country. Riders occupy every lane, filter between them, ride along the hard shoulder, and ride along the hard shoulder in the wrong direction. None of that changes where the law puts you, and none of it changes the fact that the left lane is where a rider is legally expected to be and where a Thai driver will look for you.

• Where motorbikes belongLeftmost lane (s.35)
• Lane splittingNot a defined offence
• Riding against the flowUp to 2,000 baht
• Motorways and expresswaysBanned at every engine size

What the penalty actually is

You will see it written elsewhere that riding outside the left-hand lane carries a fine of up to 2,000 baht. That is a conflation of two different things and we are not going to repeat it. The 2,000 baht ceiling introduced by the 2022 amendment attaches to driving against the flow of traffic. The traceable penalty for a section 35 breach is 400 to 1,000 baht under section 157 as the Act was originally drafted — roughly £9 to £22, and a statutory range rather than a fixed roadside charge.

In practice, riders are almost never stopped for lane position. They are stopped for helmets and licences, which is a different subject entirely: see Thailand's helmet law and stopped without a licence in Thailand.

Filtering and lane splitting

Every visitor asks whether filtering to the front of a queue at a red light is legal. The honest answer is that the Land Traffic Act contains no offence of lane splitting as such. It is not expressly permitted and it is not expressly prohibited; it is a manoeuvre the statute does not squarely address, and police do not stop riders for it. Section 43(6) prohibits straddling a lane line, but with an exception for changing lane, and it is not applied to filtering.

What that means for you: filtering is universal Thai practice, nobody will object, and at a Bangkok junction the front of the queue is where every motorbike ends up. It is also, on balance, safer than sitting in a stationary line of traffic where you can be hit from behind.

The hard shoulder, and the wrong-way problem

The shoulder of a Thai highway is where motorbikes live. It is wide, sealed, comparatively free of cars, and on a long straight highway it feels like the safest place on the road. It has one enormous flaw: it carries traffic in both directions.

Riding the shoulder against the flow is common. It is done to reach a shop a hundred metres back, to avoid riding two kilometres to a U-turn slot and two kilometres back, and simply out of habit. Since the 2022 amendment, driving against the flow of traffic carries a maximum of 2,000 baht — roughly £45 — and it is one of the ten offences the Royal Thai Police named for strict enforcement from April 2026.

Where motorbikes may not go at all

Motorcycles are banned from Thailand's motorways and expressways — all of them, at every engine size. There is no large-capacity exception of the kind some countries operate. The legal route to the ban is section 139, which lets a traffic officer prohibit categories of vehicle, together with the regulations on traffic in special lanes, and the reported fine for riding on an expressway is up to 1,000 baht.

This matters for route planning more than for enforcement. If you are riding from Bangkok towards the coast or the north, the toll network is closed to you and you will be on the ordinary highway alongside heavy traffic. Thailand's expressways and motorways explained sets out which roads are which, and Highway 4 is a good example of the alternative you will actually be using.

Driving on the pavement is prohibited under section 43(7), with exceptions only for a pram or a wheelchair. Riders do it anyway in Bangkok, particularly motorbike taxis, and it is not something a visitor should copy.

Sharing the left lane: what is in there with you

The left lane is the legal home of motorcycles, and also of trucks, buses and songthaews. That combination is the whole difficulty.

A songthaew stops wherever a passenger wants to get off, with no signal and no warning, in the left lane. A bus pulls in and out of the same space. A truck turning left will swing right first and will not see a bike alongside it. Add parked cars, food carts, dogs and pedestrians and you have a lane that is nominally yours and practically an obstacle course.

The riding position that works is left-of-centre within the lane, not hugging the kerb: far enough left to be out of the way of faster traffic, far enough right that you have somewhere to go when something stops in front of you and that drivers can see you in their mirrors. Kerb-hugging is the instinct of a nervous rider and it removes your escape route.

Carrying a passenger

Section 121 requires the rider to sit astride the saddle and permits a passenger only where the vehicle's registration certificate allows it, seated behind the rider on the pillion or in a sidecar. Both rider and passenger must wear a helmet, and the rider commits a separate offence by riding while the passenger is unhelmeted — see passenger helmets in Thailand.

Practically, two-up on a 110cc scooter changes the machine completely: it accelerates far more slowly, brakes over a longer distance and is much less stable in a swerve. That has direct consequences for U-turns onto fast roads and for overtaking. Carrying a passenger on a scooter in Thailand covers the handling side.

Frequently asked questions