Thailand's long mountainous border with Myanmar continues south from the north into western Thailand with the Tenasserim Hills, known in Thailand as Thio Khao Tanaosi (เทือกเขาตะนาวศรี). The geography of the western region of Thailand, like the north, is characterised by high mountains and steep river valleys.
Western Thailand hosts much of Thailand's less-disturbed forest areas. Water and minerals are also important natural resources. The region is home to many of the country's major dams, and mining is an important industry in the area.