Southeast Asia southeast asian agriculture Southeastern Asia is a subregion of Asiaconsisting of the countries that are geographically south of China and Japaneast of Indiasoutheast asian agriculture of Papua New Guineaand north of Australia. The region is the only part of Asia that lies partly within the Southern Hemispherealthough the majority of it is in the Northern Hemisphere. In contemporary definition, Southeast Asia consists of two geographic regions:. The region lies near the intersection of geological plateswith both heavy seismic and volcanic activities. The Sunda Plate is the main plate of the region, featuring almost all Southeast Asian countries except Myanmar, northern Thailand, northern Laos, northern Vietnam, and northern Luzon of the Philippines. The mountain ranges in Myanmar, Thailand, and peninsular Malaysia are part of the Alpide beltwhile the islands of the Philippines are part of the Southeast asian agriculture Ring of Fire.