The Tai Phuan or Phuan people are a Buddhist Tai-Lao ethnic group that migrated to Laos from southern China, and had by the 13th century formed the independent principality of Muang Phuan at the Plain of Jars, with Xieng Khouang (contemporary Muang Khoun) as the capital. They prospered from the overland trade in metals and forest products. In the mid-14th century, Muang Phuan was incorporated into the Lane Xang Kingdom under King Fa Ngum.
Although they had to pay tax and tribute to Lane Xang, the Phuan population were able to retain a high degree of mandala-model autonomy. During the 16th century, expressive Buddhist art and architecture flourished. The capital was dotted with temples in a distinct Xieng Khouang style, i.e., simple low roofs with a characteristic ‘waist’ at the foundation. In 1930, Le Boulanger described it as ‘a large and beautiful city protected by wide moats and forts occupying the surrounding hills and the opulence of the sixty-two pagodas and their stupas, of which the flanks concealed treasures, obtained the capital a fame that spread fear wide and far[this quote needs a citation].”
After the Kingdom of Siam, contemporary Thailand, extended control to Lao territories east of the Mekong in the 1770s, Muang Phuan became a Siamese vassal state while maintaining tributary relations with Dai Viet (Vietnam). To exert greater control of the lands and people of Muang Phuan, the Siamese launched three separate campaigns (1777–79, 1834–36 and 1875/76) to resettle large parts of the Phuan population to the south in regions under firm Siamese control. Subsequently in the 1870s, invasions by Haw marauders (splinter groups from the failed Taiping Rebellion in Southern China,) plundered Luang Prabang and Xieng Khuang, and desecrated and destroyed the temples of the Phuan region.
The Franco-Siamese treaties of the 1890s placed Xieng Khouang under colonial rule as part of French Indochina until briefly after World War II.