The year 1881 was an historic one for Thai telecommunications, when the first simple telephone line was constructed for national security. It was during the reign of King Chulalongkorn the Great. Thailand's telecommunication service then took root and has since been successively developed to its current modern status.

By the mid-1980s, Thailand had an average density of one telephone per hundred inhabitants. This density was better than the average of 0.7 for the developing countries in the East Asia region, although it was still lower than Malaysia with 3.3, South Korea with 7.8, Taiwan with 14.6, and Singapore with 26.5. Even Bangkok, which had the most developed telephone service in the country, had only a density of 5.4 telephones per 100 inhabitants. Overall, only 25 percent of the population had access to telephone services. There were about 5,800 local and long- distance pay (coin box) telephones in the capital city and 750 in provincial towns. About 4,500 pay telephones were to be added in Bangkok and 1,500 in provincial towns. About 62 percent of the country's telephone lines were connected to business and government subscribers and the rest to residential subscribers. Business lines accounted for 83 percent of total calls and revenues.

TOT has continued expanding its network by various means of self-finance, including bonds and conventional loans. Nevertheless, various expansion projects were unable to produce enough supply to match demand. In early 1990, the government and TOT jointly decided to issue an international invitation to the private sector to invest in a project for three million telephone lines' expansion, using the "build-transfer-operate" (B-T-O) concept. The excellent response brought two consortia to work with TOT. This urgent measure to reduce telephone shortage was a unique undertaking in which private firms, Thai and foreign joint ventures, were considered TOT's full partners in expansion projects for the first time.

Two major entities were responsible for the Thai telecommunication and postal services under the supervision of the Ministry of Communications. The Telephone Organization of Thailand (TOT) was responsible for the domestic telephone services; for international telephone services to several neighboring countries, such as Malaysia and Laos; and for leasing circuits for domestic point-to-point transmission of voices, telegraph, radio, and television.

The Communication Authority of Thailand (CAT) was responsible for postal service, international telephone service to countries not served by TOT, all telegraph and telex services international lease circuits, domestic radiotelephone links to some isolated areas, and telephotographic and facsimile services.

A committee in the Ministry of Communications coordinated the services and investment of TOT and CAT, although the two were state-owned autonomous operations. Numerous government agencies and large private industrial and commercial entities operated their own radio-telephone networks.