In Thailand, an area code is usually shared by several provinces and roughly follows provincial borders.

Fixed-line subscriber numbers are six digits in Thailand (except Bangkok, Nonthaburi, Pathum Thani, and Samut Prakan, i.e., area code 2).

Prior to 1980, subscriber numbers were six digits in Bangkok, Nonthaburi, Pathum Thani, and Samut Prakan.

In Bangkok, Nonthaburi, Pathum Thani, and Samut Prakan, the second digit of a subscriber number identifies the service provider, which is almost always National Telecom (NT), as NT holds a near-monopoly of the Thai fixed-line market.

Through a series of mergers, there are currently three major mobile phone operators: AIS, True and DTAC.