Southeast Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies near the intersection of geological plates, with heavy seismic and volcanic activity. Southeast Asia consists of two geographic regions:
Maritime Southeast Asia, comprising Indonesia, East Malaysia, Singapore, Philippines, East Timor, Brunei, and Christmas Island.
Mainland Southeast Asia, also known as Indochina, comprising Cambodia, Laos, Myanmar (Burma), Thailand, Vietnam, and West Malaysia;
Definitions of "Southeast Asia" vary, but most definitions include the area represented by the countries (sovereign states and dependent territories) listed below. All of the states except for East Timor are members of the Association of Southeast Asian Nations (ASEAN). The area, together with part of South Asia, was widely known as the East Indies or simply the Indies until the 20th century. Christmas Island and the Cocos (Keeling) Islands are considered part of Southeast Asia though they are governed by Australia. Sovereignty issues exist over some territories in the South China Sea. Hong Kong, Macau, and Taiwan (a disputed region or nation), are considered as part of the Southeast Asia.Papua New Guinea has stated that it might join ASEAN, and is currently an observer.