Do you need a visa to visit Thailand?
In short, probably not.
For trips under 30 days, citizens of 48 countries — including the United States, Canada, and much of Europe — do not need a visa to travel as a tourist to Thailand. Citizens of countries with a bilateral agreement with Thailand may also enter without a visa, whether for as few as 14 days (citizens from Cambodia) or as many as 90 (citizens of Argentina, Brazil, Chile, South Korea, and Peru).
All visa-exempt visitors must be carrying cash at their entry to demonstrate they have sufficient funds to travel in Thailand: 10,000 Baht (just under $300 USD) per person or 20,000 Baht (just under $600 USD) per family.
For visitors who wish to stay longer than 30 days, they may apply for a 30-day extension in Bangkok, at the Thai Immigration Bureau office, or apply for a 60-day tourist visa at a Royal Thai Embassy before entering Thailand. A person traveling on a 60-day tourist visa may apply for a 30-day extension upon arrival in Thailand, but tourist visas are capped at 90 days. For travelers wishing to stay even longer, they should consider other types of visas. Both the 60-day tourist visa, as well as the 30-day extension, require a 1,900 Baht (about $55 USD) fee.
The U.S Embassy and Consulate in Thailand strongly recommends that visitors not overstay their visas, reporting on their website that “Thai police have been known to sweep areas frequented by low-budget travelers and arrest those who have overstayed their visas.” Arrested travelers are sometimes held in an Immigration Detention Center until they are able to pay an overstay fine as well as a ticket out of Thailand. Those fines begin at 500 Baht (about $15 USD) per day, up to a maximum of 20,000 Baht (just under $600 USD). Travelers who remain in Thailand for more than 200 days after their tourist visa has expired may also be subject to jail time prior to deportation.