Thailand, a member of the UN since 16 December 1946, is the headquarters for ESCAP and belongs to all the nonregional specialized agencies. Bangkok has served as regional headquarters for several other UN agencies, and for the former Southeast Asia Treaty Organization (SEATO). Thailand is identified more closely than most Asian countries with the Western nations largely because of its alliance with the US. The country is a member of the Asian Development Bank, Asian and Pacific Council, ASEAN, the Association of Natural Rubber Producing Countries, G-77, and the International Tin Council. Thailand is a member of the WTO, and a signatory of the Law of the Sea.
Thailand is a participant in the Colombo Plan, and it receives economic aid from UN agencies for agricultural, industrial, and health projects. US assistance has been a vital factor in Thailand's economic development since World War II. Although never engaged in direct combat on Thai soil, the United States has been Thailand's paramount military ally in recent decades, supplying funds, equipment, advisers, and large-scale training programs for personnel. On order of the Seni government, the US military presence in Thailand was almost completely withdrawn by mid-1976, although some US assistance, including military aid, continued.
Prior to the military and political upheavals of the 1970s, Kampuchea (known as Cambodia until 1976 and again from 1989), Laos, Thailand, and the Republic of Vietnam had been cooperating on the development of the lower Mekong Basin in terms of hydroelectric power, irrigation, navigation improvement, and flood control. The Greater Mekong Subregion (GMS) has a population of approximately 245 million and covers an area approximately 2.3 million sq km (0.88 million sq mi). Progress on GMS projects moved forward in 1992 when Thailand, Cambodia, Myanmar, Laos, Vietnam, and the Yunnan Province of China engaged in closer cooperation. The goal was to facilitate economic growth and improve the standard of living in the Mekong region by greatly expanding trade and investment. Transportation, including cross-border roads, and power generation and distribution are all priorities. In addition to and in support of GMS projects, in 1995 Thailand, Cambodia, Laos and Vietnam established the Mekong River Commission (MRC) to coordinate development in the region.