Section 61 of the Highway Act published in 1992 outlines the gross combined weight of all types of vehicles to be used on public highways. Please see reference below.
Remarks: For No. 3.4, for a prime mover with 12 tyres towing a tri-dem semi-trailer, there are two allowances.
Allowance 1: If the center of the king pin and the first axle is greater than 8 meters, then the maximum GCW allowed is at 50.5tons.
Allowance 2: If the center of the king pin and the first axle is less than 8 meters, then the maximum GCW allowed ranges from 45 – 49 tons depending on this distance per below schedule.
| Distance between center of king pin to center of first axle | Maximum GCW Allowed | |
| 4.5 – 6 meters | 45 tons | |
| 6 – 7 meters | 7 – 8 meters | 49 tons |
Information Updated : April 2016
Source: Department of Land Transport, Thailand