can you name some places that come under the southern region you mentioned?
China, India and Australia are some of them.
Southeast Asia
Southeast Asia or Southeastern Asia is the southeastern region of Asia, consisting of the regions that are geographically south of China, east of the Indian subcontinent and north-west of Australia. 
where are the philippines located on the world map it is in Southeast Asia, situated in the western Pacific Ocean. was it colonised by anyone? Yes, by a Spanish explorer "Miguel López de Legazpi"
wiki:19581121
Southeast Asia [SEP] Introduction
Southeast Asia or Southeastern Asia is the southeastern region of Asia, consisting of the regions that are geographically south of China, east of the Indian subcontinent and north-west of Australia. 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. The region is the only part of Asia that lies partly within the Southern Hemisphere, although 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 plates, with both heavy seismic and volcanic activities.