Wen Dan

Wén Dān (Chinese: 文單; Thai: เหวินตัน), proposed Bhavapura,^: 59 was a group of ancient Mon political entities that existed around the 6th–10th centuries CE in the interior of mainland Southeast Asia scattered around the central Mekong Valley in the present-day northeast Thailand. It was mentioned in the Chinese annals of the Tang period (618-907 AD) as a dependency on the trans-Mekong trade route from the ancient city of Chiaochih (jiāo zhǐ 交趾; Giao chỉ; near the present-day Vinh of Vietnam) to India.^: 25–72 It sent representatives to China in 717, 750, 753, 771, 779, and 799. Some scholars identify Wen Dan with Bhavapura and believe it was the origin of the united Chenla.^{: 59, 123} However, this theory remains disputed, as some argue that Chenla probably formed in the southern Tonlé Sap Basin, rather than in Northeast Thailand or Southern Laos.^: 29–30

Initially, Wen Dan was believed to be Vientiane,^: 16 but according to the location given in the Chinese annals as well as archaeological evidence, it is supposed to be in the Chi River basin, centered in Kantharawichai, with Mueang Fa Daet Song Yang as outer center and Champasri as the vassal. Several historical evidences supports the connection between Wen Dan and Si Thep in central Thailand.^: 91–92 The Chinese text Tang Huiyao mentions Wen Dan as a state located 6 days' travel by land northwest of Keoi Lau Mì.

According to the Dvaravati Buddhist boundary stones (Bai sema) dated the 8th century found on Mt. Kulen, Woodward (2003) proposes that Wen Dan once controlled the Angkor region before Jayavarman II proclaimed the independence of the Kambujadesa from Java in 802.^: 87–88 Jayavarman II probably either defeated Wen Dan and then moved the capital from Indrapura to Yaśodharapura to the north,^: 87 or formed ally with the communities in Mun and Chi watersheds to against Si Thep to the west.^: 93