relations between the two countries had always been marred by discord, which resulted from bitter rivalry to gain control of the area of what is today Laos and Cambodia. In the 19th century, Thailand (then known as Siam) had fought a series of wars with the Nguyễn dynasty which then ruled over Vietnam over control of Cambodia. This rivalry will only temporarily subside when French colonists stepped in and gradually building an establishment in Southeast Asia, known as French Indochina. During the Vietnam War, Thailand was aligned with South Vietnam and the United States and the U Tapao Air Base was used as a base for USAF aircraft. During the Fall of Saigon in 1975, fleeing South Vietnamese pilots arrived at U Tapao before fleeing to other countries. In 1979, when the Khmer Rouge government in neighbouring Cambodia was toppled, this had raised concerns in Thailand and the Thai government quickly allied itself with the Khmer Rouge, later the CGDK, in fear of Vietnamese expansionism. In fact, Thailand was foremost among the ASEAN, of which it is part of, in opposing the Vietnamese invasion of Cambodia. Cambodian refugees soon stayed at border camps straddling the Thai-Cambodian border, and these camps are often controlled by the Khmer Rouge or the CGDK. In the years that followed, Vietnam launched a series of raids on the camps and Vietnamese troops often penetrated into Thai territory and shelled Thai border villages and towns. Americas Europe Oceania Thai diplomatic missions Royal Thai embassies and consulates Permanent missions Thailand economic and trade office International organization participation APEC, AsDB, ASEAN, BIMSTEC, CP, ESCAP, FAO, G-77, IAEA, IBRD, ICAO, ICFTU, ICRM, IDA, IFAD, IFC, IFRCS, IHO, ILO, IMF, IMO, Inmarsat, Intelsat, Interpol, IOC, IOM, ISO, ITU, NAM, OAS (observer), OPCW, PCA, UN, UNCTAD, UNESCO, UNHCR, UNIDO, UNIKOM, UNITAR, UNMIBH, UNTAET, UNU, UPU, WCL, WCO, WFTU, WHO, WIPO, WMO, WToO, WTrO See also List of ambassadors of Thailand to Chile List of ambassadors of Thailand to Mexico List of diplomatic missions in Thailand References Further reading Busbarat, Pongphisoot. "Thailand's foreign policy towards neighbouring countries and ASEAN." in Routledge Handbook of Contemporary Thailand (Routledge, 2019) pp. 431–446. Chachavalpongpun, Pavin. Reinventing Thailand: Thaksin and his foreign policy (Institute of Southeast Asian Studies, 2010). Chambers, Paul, and Poowin Bunyavejchewin. "Thailand's foreign economic policy toward mainland Southeast Asia." (2019). online Guan, Ang Cheng. Southeast Asia's cold war: An interpretive history (U of Hawaii