A majority of visitors are issued two to four week entry permits on arrival, upon
presentation of a passport and a ticket for a return or onward journey.
Entry
permits cannot be extended while you are in Thailand. It is advisable to check
with a Thai embassy or consulate in your country before departure.
If you are
planning a longer stay, apply for either a 60-day tourist visa or 30-day
transit visa from Thai embassies and consulates overseas. These can be extended
at the Immigration Office in Bangkok for a nominal fee.
View visa requirements from the Ministry of Foreign Affairs, Kingdom of Thailand