Requirement to be double vaccinated confirmed now from the 9th January. The requirement has now been passed to the airlines and they are already updating their websites. Children under 18 exempt. Johnson and Johnson single dose is ok. Recovery certificates less than 6 months old accepted.
TLDR : Answer Summary
Starting January 9, 2023, Thailand will require travelers to present proof of being fully vaccinated against COVID-19. Children under 18 are exempt from this requirement, and the Johnson and Johnson single-dose vaccine is accepted, along with recovery certificates that are less than six months old. Airlines are updating their websites to reflect these new guidelines, although the official announcement has yet to appear in the Thai gazette.