Xiān

Xiān (Chinese: 暹) or Siam (Thai: สยาม) was a confederation of maritime-oriented port polities along the present Bay of Bangkok,^: 39, 41 including Ayodhya, Suphannabhum, and Phip Phli,^: 37 as well as Nakhon Si Thammarat (Ligor), which became Siam in the late 13th century. Previous studies suggested that Xiān in Chinese dynasty records only referred to Sukhothai, ^{: 140 : 102} but this presupposition has recently been rebutted.^: 37–9

Xiān was formed from city-states on the west Chao Phraya plain after the decline of Dvaravati in the 11th century. In 1178, the region was mentioned in the term San-lo 三濼,^: 290 as recorded in the Chinese Lingwai Daida,^: 288 in which Thai scholars suggest it was plausibly referred to Chaliang's new center, Sawankhalok.^: 8

Xiān or Siam, which was also recorded as Suphan Buri and Nakhon Si Thammarat in the late 13th century, joined a federation with Lavo in 1351; this led to the formation of the Ayutthaya Kingdom with the federal seat at Ayutthaya. Phip Phli was demoted to a frontier city following the federative formation and was then governed by Suphan Buri, which was completely annexed into the Ayutthaya Kingdom in 1438, whereas Nakhon Si Thammarat maintained its vassal status throughout the Ayutthaya and Thonburi eras with short periods of independence and was demoted to Rattanakosin's province in 1782.

However, modern scholars suggest that the term Xiān mentioned in several Chinese and Đại Việt texts from 1149 until the official establishment of the Ayutthaya Kingdom in 1351 was potentially Lavo's new capital Ayodhya^: 46 instead of Sukhothai Kingdom, Suphannabhum, and other initial Siamese polities.