VijayarÃÂja () was a tenth-century Siamese ruler known primarily from the Ayutthaya Testimonies, which identify him as exercising authority over Phitsanulok and Phetchaburi. The text presents him as a descendant of the Padumasà «riyavaá¹Âà Âa dynasty and states that he ascended the throne of Phitsanulok at the age of fifteen following the death of his elder brother, Viá¹£á¹ÂurÃÂja. VijayarÃÂja is further said to have shifted his political center southward, founding Phra Nakhon Phichai Buri (), generally identified with present-day Phetchaburi, which thereafter functioned as his principal seat of power.
According to the same source, VijayarÃÂja was married to Queen à ÂrëkanyÃÂrÃÂjadevë (), by whom he had a son, à Ârësiá¹Âha, who succeeded him upon his death in 1027. The Ayutthaya Testimonies attribute a reign of forty years to VijayarÃÂja. His reign was contemporaneous with the period during which Angkorian authority asserted political influence over the eastern Menam Valley.
The Ayutthaya Testimonies also record a contemporaneous dynastic realignment in the upper Mae Klong basin during VijayarÃÂjaâÂÂs period of authority at Phetchaburi. This transition is located at Mueang Sing, identified with Jayasimhapuri in the Preah Khan Inscription (K. 904), situated along the upper Khwae Noi River, a tributary of the Mae Klong River. The text states that a new ruling lineage founded by EkarÃÂja () supplanted the earlier dynasty of BodhisÃÂra (). This lineage is said to have continued for three further reignsâÂÂBaramatiloka (), à Ârëbhà «parÃÂja (), and JatirÃÂja. The last of these rulers, JatirÃÂja, is described as a relative of a descendant of VijayarÃÂja, Pra Poa Noome Thele Seri, who is said to have succeeded him around the 1160s. The preceding dynasty at Jayasimhapuri is recorded as having comprised four rulers: RÃÂmeà Âvara (), BaramarÃÂja (), MahÃÂcakravartin (), and BodhisÃÂra.