town, northwestern Laos. The town is situated about 10 miles (16 km) south of the Chinese border and about 50 miles (80 km) east of the border with (Myanmar) Burma, in the upper Tha River valley. It is linked to eastern Myanmar and Louangphrabang (95 miles 【153 km】 southeast) by highways.

The surrounding region is predominantly mountainous, with the uplands being occupied by Lao-Theng (Lao-Theung; Mountain Mon-Khmer) peoples such as the Lamet and Khün, who constitute the majority of the populace of this area. Other minor mountain peoples are the Lolo and Akha (Ko) groups. The lowlands are inhabited by rice-farming Lü peoples closely related to the predominant valley Lao.

The Tha River, for which the town is named, rises on the Chinese border and joins the Mekong southeast of Ban Houayxay (Fort Carnot). In addition to teak and other forest products, there are unexploited lignite and copper deposits on the Tha River, as well as alluvial gold, sapphires, and zircons on the watercourses near Ban Houayxay.