Isan's total population as of 2010 was 21,305,000.
Forty percent of the population is concentrated in the provinces of Khorat, Ubon Ratchathani, Udon Thani, and Khon Kaen, known as "big four of Isan".
These provinces surround the four major cities of the same names.
As of 2010, their populations were: Khorat 142,169; Udon Thani 137,979; Khon Kaen 113,828; and Ubon Ratchathani 83,148.
However, as of 2010 only 50 percent of the region's population lived in municipal areas.
Kalasin was the most urbanised province (with almost 100 percent in municipal areas), and Roi Et the least (2.8 percent).
Thus, the population is still largely rural, but concentrated around the urban centres.

The main language of the region is Isan, a dialect of the Lao language.
Northern Khmer, a dialect of the Khmer language of Cambodia, is also spoken in the southeast.
Standard Thai is understood by everyone and is used for all official matters.
The number of speakers of Isan has been estimated at between 15–23 million, the majority of those living in Isan.

The Khorat dialect, spoken by around 10,000 people, occupies a linguistic position somewhere between Lao and standard Thai.

There is a substantial Khmer minority, concentrated in the southern provinces of Buriram, Surin, and Sisaket, and some Vietnamese refugees in Mukdahan and Nakhon Phanom.

Other languages spoken in Isan, mainly by tribal minorities, are as follows:
Isan's total population as of 2010 was 21,305,000. Forty percent of the population is concentrated in the provinces of Khorat, Ubon Ratchathani, Udon Thani, and Khon Kaen, known as "big four of Isan". These provinces surround the four major cities of the same names. As of 2010, their populations were: Khorat 142,169; Udon Thani 137,979; Khon Kaen 113,828; and Ubon Ratchathani 83,148. However, as of 2010 only 50 percent of the region's population lived in municipal areas. Kalasin was the most urbanised province (with almost 100 percent in municipal areas), and Roi Et the least (2.8 percent). Thus, the population is still largely rural, but concentrated around the urban centres.
The main language of the region is Isan, a dialect of the Lao language. Northern Khmer, a dialect of the Khmer language of Cambodia, is also spoken in the southeast. Standard Thai is understood by everyone and is used for all official matters. The number of speakers of Isan has been estimated at between 15–23 million, the majority of those living in Isan.
The Khorat dialect, spoken by around 10,000 people, occupies a linguistic position somewhere between Lao and standard Thai.
There is a substantial Khmer minority, concentrated in the southern provinces of Buriram, Surin, and Sisaket, and some Vietnamese refugees in Mukdahan and Nakhon Phanom.
Other languages spoken in Isan, mainly by tribal minorities, are as follows:
Isan