I've recently noticed a number of cars sporting "Western translations" of the Thai script of their number plates along with the place of registration, in the form of black and white stickers on front and rear.

Anyone know why? They always seem to be new cars.

To cross the border into Malaysia you need your blue - or green - book translated by the DLT into English. You also need a sticker - front and back - to put on your car displaying the roman translation. Bikes only one - in front. Some say that the DLT translation is not required - anyone can translate. But in all my crossings I have never had an issue - always DLT

White on black background sticker is for going south into Malaysia, there are various transcription system with the province being transcribed as well for example you might get Aa 1234 BKK

 

there is another, metal plates valid for Laos, Vietnam and Cambodia, looks like the Thai plates with English script eg: AB 1234 with Thailand 01 (the number being the province 01 for Bangkok) Replacing the กรุงเทพ underneath, this 'English' plate although issued by the DLT is not valid for driving within Thailand,