The degree of ethnic variation within Pacific Asia varies enormously but in general the situation becomes more complex from northeast to southwest. In a way this is not surprising since it is in the Southeast Asian region that most population movement has occurred. In the past such movement affected the mainland and the islands in different ways. On the former, Vietnamese, Thai, Khmer and Burmans contended for dominance as economic or political situations changed. Within the Southeast Asian archipelago the dominant Malays were supplemented and strongly influenced by relatively small numbers of Arab and Indian traders. Indeed, the major influences in pre-colonial Southeast Asia were from cultures that did not necessarily have a large physical presence, viz. the Indian and Chinese governmental structures and the Islamic religion.
However, during the long mercantile colonial period, as trade and commercial activity increased, there emerged a growing Chinese presence in the cities of the region. Whilst indigenous populations tended to concentrate on commodity production, the local assembly and transport of these commodities were increasingly assumed by expatriate Chinese who had both the inclination for, and experience of, this work. However, few regarded themselves as permanent residents of the ports in which they operated; their loyalties lay firmly with their ancestral homeland.