Figure 7. Topography and Drainage.
Thailand’s 514,000 square kilometers lie in the middle of mainland Southeast Asia. The nation’s axial position influenced many aspects of Thailand’s society and culture. The earliest speakers of the thailand/th_glos.asp#Tai"> Tai (see Glossary) language migrated from what is now China, following rivers into northern Thailand and southward to the Mae Nam (river) Chao Phraya Valley. The fertile floodplain and tropical monsoon climate, ideally suited to wet-rice (thamna) cultivation, attracted settlers to this central area rather than to the marginal uplands and mountains of the northern region or the Khorat Plateau to the northeast. By the twelfth century, a number of loosely connected rice-growing and trading states flourished in the upper Chao Phraya Valley. Starting in the middle of the fourteenth century, these central chiefdoms gradually came under the control of the kingdom of Ayutthaya at the southern extremity of the floodplain. Successive capitals, built at various points along the river, became centers of great Thai kingdoms based on rice cultivation and foreign commerce. Unlike the neighboring Khmer and Burmese, the Thai continued to look outward across the Gulf of Thailand and the Andaman Sea toward foreign ports of trade. When European imperialism brought a new phase in Southeast Asian commerce in the late 1800s, Thailand (known then as thailand/th_glos.asp#Siam"> Siam--see Glossary) was able to maintain its independence as a buffer zone between British-controlled Burma to the west and French-dominated Indochina to the east (see The Bangkok Period, 1767-1932 , ch. 1).