Used to be show a foreign license and or a IDP no written test
NOw
The Department of Land Transport has drafted new regulations stating that international driving permits can no longer be used as proof for obtaining a temporary driver’s license. Foreign nationals will now be required to pass a written test to qualify for the license.
Temporary driver’s license: Applicants cannot use an international driving permit as evidence for obtaining a temporary driver’s license.
Foreign nationals seeking temporary licenses: If a foreign applicant uses a valid foreign driver’s license for the same vehicle type, they will still be required to take the written test (previously exempted from the written and driving tests). The license will remain valid for two years, as before.
The use of a foreign-issued driver’s license, which is still valid, or an international driving permit under agreements to which Thailand is a party, will no longer be accepted as evidence for obtaining a personal driver’s license. The validity of the personal driver’s license has been extended from two years to five years. This applies to cases where the applicant has previously held a temporary personal driver’s license that has expired.
https://www.nationthailand.com/blogs/news/general/40051501