Depends on the airline some are strict, no visa without a return might not let you on , immigration rarely bother. Just buy a cheap bus ticket to laos, all you need to prove is your leaving the country before 60 days
James Green really? my mate does it all the time called me once from Manchester Airport staff wouldn't let him fly i booked him a bus ticket he went back let him on the plane
Just go the airport, immigration have already announced they expect this and will help, worst case you get 500 baht fine, but they have already stated they will be tolerant due to circumstances.
The ask:thailand community, consisting of multiple Q/A groups with over 100,000 members, powers this platform. It is not an official government resource. Our members actively contribute to this resource, and while we strive for accuracy, we cannot guarantee its complete reliability. Assistance to travelers is provided as a community service.