Thailand tightens rules on public bus modifications

Thailand has introduced stricter controls on modifications to public passenger vehicles, requiring official approval and engineering supervision before work begins on a bus body or chassis.

The two Department of Land Transport (DLT) announcements took effect on 1 July 2026. Operators or owners who alter a vehicle without notifying the registrar face fines of 2,000 to 50,000 baht, up to six months in prison, or both, and may have the vehicle seized for inspection.

Deputy government spokesperson Ploythale Laksameesangchan said on 30 July 2026 that the measures were intended to ensure buses on Thai roads have sound, strong and properly standardised structures.

The regulations are formally titled the 2025 criteria and conditions for permission to modify or change the body of a vehicle used for passenger transport, and the second 2025 amendment to rules governing changes to vehicle equipment or components.

Approval before any work starts

Before changing a vehicle body or chassis frame, the owner or operator must seek approval from the DLT. Required evidence includes documents relating to the operator and vehicle, photographs showing its condition before work starts, design drawings and a design certification from an engineer qualified at least to professional engineer level.

During the modification, work must follow the approved drawings only. Operators must retain photographs of the exterior and interior, including body structural pillars where applicable, or images of the chassis, wheel axles and steering linkage.

They must also provide certification and photographs showing the supervising professional engineer with the vehicle while it is being modified.

If work differs from the approved drawings, it must stop immediately and the vehicle must be corrected. Where the design itself needs changing, the owner must apply to the registrar for permission to amend the drawings before work can resume.

The DLT has also expressly banned welding or modifying wheel axle areas beyond the manufacturer's design.

Only registered workshops may carry out work

Body-building and chassis-modification workshops must register with the DLT before taking on this work. To qualify, a workshop must hold an R.ng.4 factory licence and/or ISO9001 quality certification covering vehicle production or assembly, as applicable.

Registered workshops can be checked on the department's website at https://aeb.dlt.go.th/th. Workshops that have not registered cannot carry out body or chassis modifications, or complete the related registration process.

After the work is finished, the owner must submit evidence to the DLT for registration, including photographs of the completed body or chassis with the engineer, and an engineer's certificate confirming that the vehicle is structurally sound and matches the approved design.

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31 July 2026