Do Thailand or airlines currently enforce having an onward/return flight?
I usually travel on oneways without having onward travel booked yet. I plan to enter as a tourist for 4 weeks with a US passport. Arriving in EVA Air at BKK.
TLDR : Answer Summary
Most airlines do enforce a policy requiring travelers to have a return or onward flight booked, which can be verified directly with the airline. Additionally, Thai authorities may ask for evidence of onward travel upon entry, along with proof of sufficient funds and accommodation details.