Before the Second World War, the term "South-East Asia" was scarcely a geographic expression and was rarely used. The region of the peninsula between India and China was included in the term "Far East". Some authors called the region "Further India". During the Second World War, the Japanese Army used the term "Greater East Asia" to include countries of South-East Asia.
   

The term "South-East Asia" is credited to the Indian historian K.M. Pannikar who used it in the title of his book "Future of Southeast Asia" published in 1943. Due to military and strategic considerations during the Second World War, the region came to be regarded as a separate geographic entity and the Allied Supreme Command adopted the term "South-East Asia". By the end of the war, the term was well established and was used as a collective for the peninsula between India and China. The countries include Brunei, Burma, Thailand, Laos, Cambodia, Vietnam, Malaysia, Singapore and Indonesia. Some organizations include the Phillipines in South-East Asia.

Countries in and adjacent to the Indian subcontinent, namely, India, Pakistan, Bangladesh, Nepal, Bhutan, Sri Lanka and Maldives are considered as belonging to "South Asia"

When the formation of the World Health Organization was being discussed, the Interim Commission of the World Health Organization made some prelimiary inquiries from governments concerning their views on the delineation of areas for the regional organization of WHO. The First World Health Assembly set up a Committee in 1948 to consider the delimitation of the geographical areas. After much debate, the Committee recommended to the Assembly to delineate the areas as: Europe, Middle East, Near East and parts of North-East Africa; South-East Asia; the Far East; and Africa. The area for the Americas was included later.
           
     
The Assembly by a resolution, delineated six geographic areas for regional organizations as follows:

      Eastern Mediterranean

      Western Pacific

      South-East Asia

      Europe

      Africa (South of the Sahara)

      The Americas

The following countries were considered as belonging to the South-East Asia Region – Afghanistan, Burma, Ceylon (SriLanka), India and Siam (Thailand). The designation of the countries to the South-East Asia Region thus did not follow the generally accepted definition of South-East Asia. The Assembly in its recommendations for grouping had considered several factors. However, these criteria could not and were not applied consistently and no uniform method was employed to delineate the regions. The American and European regions were defined to inlcude whole continents; the African Region was based partly on political frontiers and partly on geographic frontiers. For the Eastern Mediterranean, South-East Asia, and the Western Pacific Region, the states and territories were enumerated. States, which were not included in this enumeration, or new Member States were assigned to the various regions by the Assembly. But the States could also request transfer from one region to another.

WHO’s Regions

The six regions into which WHO placed the countries of the world are based on geography, tempered or distempered by politics, and not on stages of development. Every region of the World Health Organization contains examples of countries at all degrees of development and no region is homogeneous in its races, religions, political or cultural organization, not in its resources, its industrial development, its trained manpower; not its diseases and health problems. Sometimes these may be a factor common or more obvious in one region than another; Eastern Mediterranean Region is largely Moslem, with whatever that implies for its health; European Region is largely industrialized; the African Region has more diseases of the "tropical" type: but these are exceptions.

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The original five members of the South-East Asia Region were: Afghanistan, Burma, Ceylon (Sri Lanka), India and Siam (Thailand). These countries had signified their consent at the First World Health Assembly in 1948 to join the South-East Asia Region when it was established.

By a resolution of the Second World Health Assembly, representatives of Member States of WHO, not having their seat of government within the Region but responsible for the conduct of international relations for territories which were within the Region, were allowed to attend the Regional Committees. It was, thus, that in the South-East Asia Region, France (representing French India), Portugal (representing Portuguese India) and the United Kingdom (representing the Maldive Islands), attended the meetings of the Regional Committee for South-East Asia, from the second to the sixteenth sessions. French and Portuguese territories in India became part of the Republic of India in 1954 and 1961 respectively. The MaldiveIslands became independent in 1965.

The original Assembly resolution in 1948 had placed Indonesia in the Western Pacific Region. But in 1950, when Indonesia joined WHO, it was transferred, at its own request, to the South-East Asian Region.

The Republic of Vietnam and the Kingdoms of Cambodia and Laos were also originally included in the South-East Asia Region by a resolution of the Third World Health Assembly. But when the Western Pacific Regional Office was established in 1951, these three countries opted to join that Region.

The Kingdom of Nepal became a member of the World Health Organization on 2 September 1953 and was formally included in the South-East Asia Region by a resolution of the World Health Assembly in 1953.

The next country to become a member of the South-East Asia Region was the Mongolian People’s Republic. It became a member of WHO on 18 April 1962, and although not belonging geographically to South or South-East Asia, it requested to be allowed to join this Region. This was formally approved by the Fifteenth World Health Assembly. However from 1 July 1995, Mongolia separated from the South-East Asia Region and joined the Western Pacific Region.

Maldives became independent on 26 July 1965. It became a member of WHO on 5 November 1965 and joined the South-East Asia Region.

In 1969, Afghanistan, one of the original members of the South-East Region, was transferred at its request and the approval of the Assembly to the Eastern Mediterranean Region because of geographical contiguity and for political reasons.

Bangladesh was East Pakistan at the time of independence of India and Pakistan in 1947. In December 1971, it gained independence and became the People’s Republic of Bangladesh. It became a member of WHO on 19 May 1972 and joined the South-East Asia Region.

The Democratic People’s Republic of Korea became a member of WHO on 19 May 1973, the first UN agency the country joined. It opted to join the South-East Asia Region.

The Kingdom of Bhutan  joined WHO on 8 March 1982.

The most recent MemberState to be included in the Region is the Republic of Timor Leste which joined WHO on 27 September,2002, and opted for joining the South-East Asia Region in May 2003.

In September 1988 the Union of Burma was named as the Union of Myanmar.

There are now eleven Member States in the WHO South-East Asia Region. They are listed below with the date which they became a party of WHO’s Constitution:
          

Names

Thailand, before the Second World War was known as Siam. During the war, the name was changed to Muang Thai (Land of the Free) or Thailand but immediately after the war, it reverted back to its original name of Siam. It was not until 1949 that the name of the country was once again changed back to Thailand, and it has remained so ever since.

Ceylon was the name of Sri Lanka till 1972. On gaining independence from Britain in 1948, the country was called the Dominion of Ceylon. In 1972, a new constitution was adopted creating a republic and the name of the country changed to Sri Lanka.

Indonesia was known as the Netherlands East Indies before the Second World War. The name Indonesia was introduced in 1945.