Previous historical and archaeological research in the Salween and Ping river basins, northwestern Thailand, tend to focus on the social and political development of the lowland or valley settlements, while upland regions have been marginalised. This presentation is part of my PhD research and it provides recent data from archaeological surveys and excavations in these regions in order to examine social formation of the highland communities since the first millennium CE. New discoveries have also raised questions about the centre-periphery model of lowland-upland relationships during the second millennium CE, as it was previously thought that lowland centres (e.g. Lanna, Ava) controlled upland areas; however, I argue that the relationship was more complicated than previously considered. To understand these relationships, I draw particularly from circular mound sites, or ring ditches, which have been identified as burials.