You can look in a few places:
1) The pink and blue registration sticker on our front windshield has the expiration date (day, thai month abbreviation, thai year). For your convenience, when you buy a car from us or renew your registration through us, we provide a registration holding sticker that has the Thai month abbreviation and Bhuddist year conversion for you.
2) Alternatively you can also find the registration renewals records in the back of your blue title book.
3) In most cases the yearly registration expiration date is the same day/year the car was original registered when bought new so you can also see that info on the vehicle info page of your blue title book.