Entry requirements for US citizens
US citizens can enter Thailand visa-free for tourism for stays under 60 days with a valid passport, and must complete the free online Thailand Digital Arrival Card (TDAC) before arrival.
The TDAC is submitted at tdac.immigration.go.th within 3 days before arrival. The US State Department advises having at least six months of passport validity from the entry date, one blank passport page, and proof of onward travel, which airlines or officials may ask to see. An extension of up to 30 days can be requested at a Thai immigration office.