Most western visitors do not require a visa to visit Thailand for a short term as tourists. Stays cannot be more than 30 days in one go and a total of 90 days within a six-month period. You will require a passport with at least six months remaining from your date of entry, alongside a return air ticket and proof that you have the equivalent of just over USD 600 to fund your stay. These details can be requested by customs officials on entry into the country.