Uthong I
Uthong I, also known as Soi La, the king of Xiān at Suphannaphum, who took over the vacant throne at Suphanburi in 1163. Uthong was also appointed by his elder brother Pra Poa Noome Thele Seri as the ruler of either Singburi or Jayasimhapuri following Pra Poa Noome Thele Seri's departure to rule Phrip Phri in 1188.
Records
The presence of Uthong I is preserved in a fragmented and often contradictory body of sources, which complicates any attempt to reconstruct his historical role. The Ayutthaya Testimonies identify him as the younger brother of Indraraja, who was equated with Pra Poa Noome Thele Seri. Yet European and Thai documents diverge over his significance and movements.The two principal French accounts—Du Royaume de Siam and Instructions Given to the Siamese Envoys Sent to Portugal —acknowledge his brother Pra Poa Noome Thele Seri, describing him as a prince from Tasoo Nacora Louang who subsequently relocated to Soucouttae/Locontàï. These works, however, make no mention of Uthong I, thereby excluding him entirely from the European record.
In contrast, the Royal emphasizes Uthong I directly, situating his origins in Mueang Chaliang. According to this account, he, together with his elder brother Pra Poa Noome Thele Seri, moved southward in the mid-12th century, and the elder brother eventually seized control of either Singburi or Jayasimhapuri in 1169. The chronicle also records that Uthong I had earlier been appointed to the throne of Suphannaphum in 1163, though, according to the Ayutthaya Testimonies, this arrangement was altered when Pra Poa Noome Thele Seri reestablished his authority at Phrip Phri. At that point, Uthong I was assigned to govern Mueang Sing, thereby consolidating authority over more than one regional center.
The conclusion of Uthong I's reign is unrecorded. Modern Thai scholars have hypothesized that he was succeeded by his nephew, Uthong II, who later became a monarch of Ayodhya, suggesting that Uthong I's reign came to an end around 1204/05. The Northern Chronicle further reports that Uthong II entrusted three major regional centers to his sons, yet Suphannaphum is conspicuously absent from this list. This omission has been interpreted as evidence that Mueang Suphannaphum, once associated with Uthong I, had diminished in importance by the early 13th century.
Suphannaphum dynasty
The political seat at Suphannaphum appears to have been left vacant following the reign of Uthong I. According to the local legend of, dated to the last half of the 1220s, Saen Pom is said to have migrated southward from the Tai polity of, located in the upper valley under the suzerainty of the Sukhothai Kingdom, to Suphannaphum, where he assumed the vacant throne. His son, Uthong III, succeeded him, thereby establishing a dynastic line subsequently known as the Suphannaphum dynasty, which continued to govern the polity until the foundation of the Ayutthaya Kingdom in 1351, when Uthong V, the Ayutthaya first monarch married Suphannaphum princess and incorporated the polity into his kingdom.This hypothesis aligns with the theory that Khun Luang Pho Ngouy—identified either as the son or the son-in-law of Uthong III and later enthroned as Borommarachathirat I, the third monarch of Ayutthaya and the first ruler of the Suphannaphum lineage—may have possessed ancestral connections to Sukhothai. Such connections are suggested by his marriage to a daughter of King Loe Thai of Sukhothai, as well as by the repeated instances of royal intermarriage between his descendants and members of the Sukhothai dynasty. Moreover, political interactions and architectural developments in Suphanburi during the Ayutthaya period indicate a close relationship between these two dynastic houses. The kinship ties between the royal families of Suphanburi and Sukhothai may therefore be traced back at least to the reign of King Ramkhamhaeng of Sukhothai.