Located on the east coast of peninsular Siam, an isthmian tract between the South China Sea and the Bay of Bengal, Tambralinga had the cosmopolitan openness associated with islands to trade and cultural influences. It was involved in maritime exchange since the late centuries b.c. , and its heartland had the highest densities of bronze drums, early Visnu images, lingas, Hindu shrines, and stone inscriptions in peninsular Siam. During its peak in the early centuries of the second millennium a.d. , according to historical documents, it sent a series of envoys to China and sent an army across the ocean to occupy the northern part of Sri Lanka. However, its early development and landscape have been less studied. This article explores the relationships between land and life in Tambralinga’s heartland, today’s Nakhon Si Thammarat Province, during the fifth to thirteenth centuries a.d. As a pioneering work on this topic in peninsular Siam, this article discusses the distributions of late prehistoric sites and early Hindu shrines in relation to geography using data from GIS-based studies, archaeological surveys and excavations, and ethnographic interviews. The results demonstrate that the landscape of Tambralinga was vital to its development. Its heartland opened out to the South China Sea, where an intensive maritime trade took place, and it had mountains in its backyard that were the source of forest products and tin, valued highly by foreign merchants. The floodplain between the shores and the mountains produced rice and cattle for the population of the kingdom. Tambralinga had beach ridges, running in the north–south direction, as the core of its landscape, which facilitated communications among clusters of communities. Rivers and walking trails provided passageways between various ecological zones and connected the kingdom to the west coast of the isthmus as well.