Southeast Asia was under Indian influence starting around 200 BC until around the 15th century, when Hindu–Buddhist influence was absorbed by local politics. India had established trade, cultural and political relations with Southeast Asian kingdoms in Burma, Thailand, Indonesia, Malay Peninsula, Cambodia and, to a lesser extent, Vietnam.
The peoples of maritime Southeast Asia — present day Malaysia, Indonesia and the Philippines — are thought to have migrated southwards from southern China sometime between 2500 and 1500 BC. The influence of the civilization of India gradually became predominant among them, and among the peoples of the Southeast Asian mainland. Indian traders, adventurers, teachers and priests continued to be the dominating influence in Southeast Asia until about 1500 CE, and Indians often ruled the earliest states in these regions. Hinduism and Buddhism both spread to these states from India and for many centuries existed there with mutual toleration. Eventually the states of the mainland became mainly Buddhist.
The Indo-Chinese peninsula was known as Suvarnabhumi or Suvarnadvipa, the land or island of gold. Indians traveled to the Far East through the land or sea routes. The land route was through Bengal, Manipur, Assam, and Burma. Regarding the sea-routes, one could start from Tamluk in Midnapore, Bengal and proceed along the coasts of Bengal, Burma, Malay Peninsula, Java etc. or start from Gopalpur (Orissa), Masulipatnam and sail across the Bay of Bengal to the Far East. Trades induced by the mineral, metals wealth were the primary reasons for this intercourse between India and the Far East. Over time trade led to political and cultural relations. Trade relations may have begun around 200-3
The first of these Indianised states to achieve widespread importance was the Kingdom of Funan founded in the 1st century CE in what is now Cambodia — according to legend, after the marriage of an Indian Brahman into the family of the local chief. These local inhabitants were Khmer people. Funan flourished for some 500 years. It carried on a prosperous trade with India and China, and its engineers developed an extensive canal system. An elite practised statecraft, art and science, based on Indian culture. Vassal kingdoms spread to southern Vietnam in the east and to the Malay Peninsula in the west.