A state enterprise under the Ministry of Transport and Communications, it incorporated the Telephone Technician Unit under the Post and Telegraph Department.

The TOT provided telephone services in the Bangkok metropolis, which included Wat Lieb, Bang Rak, Ploenchit, and Sam Sen Exchanges.

Under the deposed government of Thaksin Shinawatra (2001–2006), TOT became a corporation and plans were under way to privatise a portion of the state enterprise through an IPO on the Stock Exchange of Thailand.

General Saprang's first move as TOT chairman was to hand-pick three Army colonels and controversial Thaksin-critic Vuthiphong Priebjrivat to sit on the state enterprise's board of directors.

The Surayud government's excise tax cancellation meant that TOT and CAT Telecom would receive their full concession payments.

In August 2014, TOT was ordered by the State Enterprise Policy Commission to submit a proposal that would wind down non-core businesses, allowing it to reduce costs.