Thailand, Myanmar, Malaysia, Laos, South Vietnam and Cambodia (with Singapore included thereafter) were the founding members. These countries agreed to hold the Games biennially. The SEAP Games Federation Committee was formed.
The first SEAP Games were held in Bangkok from 12–17 December 1959 comprising more than 527 athletes and officials from Thailand, Myanmar , Malaysia, Singapore, South Vietnam and Laos participating in 12 sports
The SEAP Federation considered the inclusion of Brunei, Indonesia and the Philippines. These countries were formally admitted in 1977, the same year when SEAP Federation changed their name to Southeast Asian Games Federation (SEAGF), and the games were known as the Southeast Asian Games. East Timor was admitted at the 22nd Southeast Asian Games in Vietnam.
Participating Countries
Cambodia Debuted 1959
Laos (IOC designation: Lao People's Democratic Republic) Debuted 1959
Malaysia Debuted 1959 
Burma or Myanmar Debuted 1959
Singapore Debuted 1959
Thailand Debuted 1959
Vietnam (IOC designation: Viet Nam) Debuted 1959
Brunei (IOC designation: Brunei Darussalam) Debuted 1977
Indonesia Debuted 1977
Philippines Debuted 1977
Timor-Leste Debuted 2003
