The mountain ranges in Myanmar, Thailand, Peninsular Malaysia and the Indonesian islands of Sumatra, Java, Bali, Lesser Sunda Islands, and Timor are part of the Alpide belt, while the islands of the Philippines and Indonesia as well as Timor-Leste are part of the Pacific Ring of Fire. 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, while the Sunda Plate only includes western Indonesia to as far east as the Indonesian province of Bali. The region lies near the intersection of geological plates, with both heavy seismic and volcanic activities. Timor-Leste and the southern portion of Indonesia are the only parts of Southeast Asia that are south of the Equator.

Mainland Southeast Asia is completely in the Northern Hemisphere. Apart from the British Indian Ocean Territory and two out of 26 atolls of Maldives in South Asia, Maritime Southeast Asia is the only other subregion of Asia that lies partly within the Southern Hemisphere.

Southeast Asia is bordered to the north by East Asia, to the west by South Asia and the Bay of Bengal, to the east by Oceania and the Pacific Ocean, and to the south by Australia and the Indian Ocean. Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland China, east of the Indian subcontinent, and north-west of mainland Australia which is part of Oceania.

Asian mou tai s