dont leave it to long. More than 5-7 years overdue and they cancel the licence and trying to get another is very difficult. Bike is worthless without it
Will need a test first then you pay current year in full about 600thb then a fine for each year you missed which from memory was about 150-200thb per year missed
so if its not 100% than why wouldnt you warn someone who is clearly unsure and prepare them for that possibility so theres no big panic at check in ? Ive been asked and i had a TR