Ruma upazila on the north, Arakan (Myanmar) on the south, Chin (Myanmar) and Belaichhari upazila on the east, Alikadam and Lama upazilas on the west.

Thanchi thana was established in 1976 and was turned into an upazila in 1985. It consists of 4 union parishads, 12 mouzas and 82 villages.

Thanchi Upazila is located in Bandarban District. Upazilla(s)/Thana(s) in Bandarban are Alikadam Upazila, Bandarban Sadar Upazila, Lama Upazila, Naikhongchhari Upazila, Rowangchhari Upazila, Ruma Upazila, Thanchi Upazila.