Years back, I and a Singaporean friend went to Trat, my Singaporean friend was driving, we were checked at the the large checkpoint before Trat, they didn't accept his Singaporean drivers license, I presented the agreement regarding the use of SEA licenses allover ASEAN, they didn't accept it. He had to pay 600 THB, and we had a receipt, in Thai language, when translated the ticket said: "Expired Thai license"