Kanchanaburi in the context of Thesaban mueang

The Tenasserim Hills or Tenasserim Range (Burmese: တနင်္သာရီ တောင်တန်း, [tənɪ̀ɰ̃θàjì tàʊɰ̃dáɰ̃]; Thai: ทิวเขาตะนาวศรี, RTGS: Thio Khao Tanao Si, pronounced [tʰīw kʰǎw tā.nāːw sǐː]; Malay: Banjaran Tanah Seri/Banjaran Tenang Sari) is the geographical name of a roughly 1,700 km long mountain chain, part of the Indo-Malayan mountain system in Southeast Asia.

Despite their relatively scant altitude these mountains form an effective barrier between Thailand and Myanmar in their northern and central region. There are only two main transnational roads and cross-border points between Kanchanaburi and Tak, at the Three Pagodas Pass and at Mae Sot. The latter is located beyond the northern end of the range, where the Tenasserim Hills meet the Dawna Range. Minor cross-border points are Sing Khon, near Prachuap Khiri Khan, as well as Bong Ti and Phu Nam Ron west of Kanchanaburi. The latter is expected to gain in importance if the planned Dawei Port Project goes ahead, along with a highway and a railway line between Bangkok and that harbor.

Kayin State, formerly known as Karen State, is a state of Myanmar. The capital city is Hpa-An, also spelled Pa-An.

The terrain of the state is mountainous, with the Dawna Range running along the state in a NNW–SSE direction, and the southern end of the Karen Hills in the northwest. It is bordered by the Mae Hong Son, Tak, and Kanchanaburi provinces of Thailand to the east; Mon State and Bago Region to the west and south; and Mandalay Region, Shan State and Kayah State to the north.