A visa is fundamentally a cocument affixed into the passport issued to a foreigner by the Thai government allowing a foreigner to travel to the Kingdom and a granted permission to stay for a certain period of time. Visas can only be obtained outside of the Kingdom from a Royal Thai Embassy consulate. A visa has a validity period which denotes the period within which the visa may be used to apply for entry. The validity period is not the length of time you will be permitted to stay in the Kingdom.
A 'permission to stay' stamp is entered into your passport upon arrival intro the Kingdom. Whatever visa you hold, you will always receive this stamp. It will include the date of entry and date when you MUST leave the Kingdom or make alternative arrangements. The 'length of stay' will be dependent on what type of visa you hold.
The majority of Foreigners that enter the Kingdom without a visa will be granted a 'permission to stay 30 day' stamp only, which is free of charge. At the discretion of the immigration officer this permission to stay 30 day stamp may be extended for up to 7 - 15 days (1,900 Baht) at an immigration office after which time the holder must leave the Kingdom. This stamp is NOT a visa.
Warning: You only get 15 days at land borders
