There are four main physical-geographic regions in the country: the mountainous area of Northern Thailand, the Chao Phraya Plain, the Korat Plain and the Malay Peninsula.

An excerpt from the article 31 facts about Thailand

It is mostly a lowland country, the interior of which is occupied by the alluvial Chao Phraya Plain, stretching for 500 km. It stretches from the mountains in the north of the country to the coast of the Gulf of Thailand.

The Korat Plain occupies the eastern part of the country, its area is almost 170.000 square kilometers. From the north and east, it is bounded by the Mekong River - the longest river on the Indochinese Peninsula.

The main mountain range of Thailand is Thanon Tong Chai with the highest peak in Thailand, Doi Inthanon, with a height of 2595 m above sea level.

The coastal zone of the Malay Peninsula is occupied by lowlands, and the central part by mountains, exceeding 1000 m above sea level.