Based on the geographic topology of Thailand, the
northeastern region is separated from the central and eastern
regions by four mountain ranges. The Phetchabun,
Dong Phya Yen, and the western part of the San Kampheng
mountain ranges separate the northeastern region from the
central region, while the Phanom Dong Rak and the eastern
part of the San Kampheng mountain ranges separate the
northeastern and eastern regions (Fig. 3).