Thailand Geography & Climate

Thailand covers about 513,000 square kilometres and divides into four physical regions that shape how the country is travelled.

The central plain is the flood basin of the Chao Phraya, historically the rice bowl and the site of every Thai capital. Bangkok sits at its lower end, barely above sea level and subsiding.

The north is hill country, folded ridges running down from the Himalayan foothills and reaching 2,565 metres at Doi Inthanon. It is cooler, and the hill communities there are culturally distinct.

The northeast, Isan, is a sandstone plateau bounded by the Mekong — drier, poorer and the largest of the four.

The south runs down the Malay Peninsula with the Andaman Sea on one side and the Gulf of Thailand on the other. The limestone karst that makes Krabi and Phang Nga distinctive is the same formation that surfaces again in Vietnam's Ha Long Bay.

Thailand is tropical and runs on three mainland seasons: cool from November to February, hot from March to May, and rainy from June to October.

"Cool" is relative — Bangkok still reaches the low thirties. The genuinely cool weather is in the northern hills, where December nights can approach freezing at altitude.

The rainy season is usually a heavy downpour in the late afternoon rather than continuous rain, and it does not make travel impractical on the mainland.

The coasts run different monsoons. The Andaman coast is wettest from May to October; the Gulf coast is wettest from October to December. This is the single most useful climate fact for planning a Thai beach holiday.

March and April bring severe agricultural burning haze to the north, with air quality in Chiang Mai regularly among the worst in the world during those weeks.