Boriwen (Thai: บริเวณ) were subdivisions of three of the larger Thai monthon. Several mueang were grouped together into one boriwen. In 1908 the boriwen were renamed to changwat, which became the name of provinces countrywide in 1916.
The monthon with between three and five boriwen were Phayap, Udon Thani and Isan. Each boriwen was administrated by a commissioner (khaluang boriwen, ข้าหลวงบริเวณ). The administrative headquarters of the boriwen were located in the provincial town listed first:
Monthon PhayapBoriwen Northern Chiangmai: Chiang Rai, Chiang Saen, Papao, Nongkhwang, and FangBoriwen Western Chiangmai: Mae Hong Son, Yuam, Khun Yuam, and PaiBoriwen Northern Nan: Chiangkhong, Thoeng, Chiangkham, Chianglaeng, Chianglom, Chianghon (Khop and Kutsawadi were seceded to France in 1904)Monthon Udon ThaniBoriwen Makkhaeng: Ban Makkhaeng (Udonthani), Nongkhai, Nonglahan, Kumphawapi, Kamutthasai, Phonphisai, and RattanawapiBoriwen Phachi: Khonkaen, Chonnabot, and PhuwiangBoriwen That Phanom: Nakhon Phanom, Chaiburi, Tha Uthen and MukdahanBoriwen Sakon: Sakon NakhonBoriwen Nam Huang: Loei, Kaen Thao, Bo ThaMonthon IsanBoriwen Ubon: Ubon Ratchathani, Khemmarat, YasothonBoriwen Champassak (Bassac): Champassak (Bassac)Boriwen Khukhan: Khukhan, Sisaket, and Det-udomBoriwen Surin: Surin, and SangkhaBoriwen Roi-et: Roi Et, Mahasarakham, Kalasin, Kammalasai, Suwannaphum