Landforms and drainage divide the country more or less into four natural regions--the North, the Northeast, the Center, and the South. Although Bangkok geographically is part of the central plain, as the capital and largest city this metropolitan area may be considered in other respects a separate region. Each of the four geographical regions differs from the others in population, basic resources, natural features, and level of social and economic development. The diversity of the regions is in fact the most pronounced attribute of Thailand's physical setting.

During the winter months, in the mountainous North the temperature is cool enough for the cultivation of fruits such as lychees and strawberries. These high mountains are incised by steep river valleys and upland areas that border the central plain. A series of rivers, including the Nan, Ping, Wang, and Yom, unite in the lowlands to form the Chao Phraya watershed. Traditionally, these natural features made possible several different types of agriculture, including wet-rice farming in the valleys and shifting cultivation (see Glossary) in the uplands. The forested mountains also promoted a spirit of regional independence. Forests, including stands of teak and other economically useful hardwoods that once dominated the North and parts of the Northeast, had diminished by the 1980s to 13 million hectares. In 1961 they covered 56 percent of the country, but by the mid-1980s forestland had been reduced to less than 30 percent of Thailand's total area.

The Northeast, with its poor soils, is not favored agriculturally. The region consists mainly of the dry Khorat Plateau and a few low hills. The short monsoon season brings heavy flooding in the river valleys. Unlike the more fertile areas of Thailand, the Northeast has a long dry season, and much of the land is covered by sparse grasses. Mountains ring the plateau on the west and the south, and the Mekong delineates much of the eastern rim.

The "heartland" of the Central Thai, the Center is a natural self-contained basin often termed "the rice bowl of Asia." The complex irrigation system developed for wet-rice agriculture in this region provided the necessary economic support to sustain the development of the Thai state from the thirteenth-century kingdom of Sukhothai to contemporary Bangkok. Here the rather flat unchanging landscape facilitated inland water and road transport. The fertile area was able to sustain a dense population, 422 persons per square kilometer in 1987, compared with an average of 98 for the country as a whole. The terrain of the region is dominated by the Chao Phraya and its tributaries and by the cultivated paddy fields. Metropolitan Bangkok, the focal point of trade, transport, and industrial activity, is situated on the southern edge of the region at the head of the Gulf of Thailand and includes part of the delta of the Chao Phraya system.

The South, a narrow peninsula, is distinctive in climate, terrain, and resources. Its economy is based on rice cultivation for subsistence and rubber productio6ce ion for industry. Other sources of income include coconut plantations, tin mining, and tourism, which is particularly lucrative on Phuket Island. Rolling and mountainous terrain and the absence of large rivers are conspicuous features of the South. North-south mountain barriers and impenetrable tropical forest caused the early isolation and separate political development of this region. International access through the Andaman Sea and the Gulf of Thailand made the South a crossroads for both Theravada Buddhism, centered at Nakhon Si Thammarat, and Islam, especially in the former sultanate of Pattani on the border with Malaysia.

Thailand's regions are further divided into a total of seventy-three provinces (see fig. 8). The country's provinces have the same names as their respective capitals.

Data as of September 1987