Southeast Asia Treaty Organization SEATO's flag Map of SEATO members, shown in blue. Abbreviation SEATO Formation 8 September 1954 Dissolved 30 June 1977 Type Intergovernmental military alliance Headquarters Bangkok, Thailand Region served Southeast Asia Membership 8 states Australia France New Zealand Pakistan Philippines Thailand United Kingdom United States Non-members protected by SEATO 3 states Cambodia (until 1956) Khmer Republic (1970–1975) Laos South Vietnam Official languages 6 languages English Urdu Thai Filipino Spanish French