Pra Poat honne Sourittep pennaratui sonanne bopitra

Pra Poat Honne Sourittep Pennaratui Sonanne Bopitra (Thai: พระปฐมสุริยเทพนรไทยสุวรรณบพิตร), alternatively titled Sommedethia Ppra Pattarma Souria Naaranissavoora Boppitra Seangae (สมเด็จพระปฐมสุริยนาราณีศวรบพิตร) and widely associated with Padumasuriyavamsa (พระปทุมสุริยวงศ์), is a monarch in early Siamese historical tradition. His reign is documented in the French works Du Royaume de Siam and the Instructions Given to the Siamese Envoys Sent to Portugal in 1684, which present him as a sovereign of a polity designated Tchai Pappe Mahanacon (ไชยบุรีมหานคร). The polity has been tentatively correlated with the historical region of Phraek Si Racha, which is briefly mentioned in the Ayutthaya Testimonies as being located east of Sankhaburi. Yet, scholarly debate persists, especially since Michael Smithies proposed that Tchai Pappe Mahanacon may instead correspond to Angkor. Despite such uncertainties, the narrative of Sourittep Pennaratui provides one of the earliest genealogical frameworks for later Siamese dynasties and contributes significantly to the reconstruction of Siamese pre-Ayutthayan history.

Following the invasion by Angkor in the mid 10th century, Padumasūriyavaṁśa's descendant, Visnuraja, is reported to have migrated northward to the seat of Phitsanulok in 957 and his descendents subsequently relocated the seat back to the Phraek Si Racha region. This newly established polity became known in Chinese sources as Xiū Luó Fēn. Historical Chinese records further attest that Xiū Luó Fēn maintained dynastic and cultural affiliations with Qiān Zhī Fú, the polity associated with Si Thep. Taken together, these accounts indicate that the political activities and territorial movements of Padumasūriyavaṁśa's descendants were confined to the Menam Valley, where they founded and governed several urban centers, such as Oghapurī (โอฆะบุรี; modern Phichit), Vijaya (พิไชย; modern Thung Yang), Vicitraprakāra (พิจิตรปราการ or วิเชียรปราการ; modern Kamphaeng Phet), Phrip Phri, Chai Nat, Sing Buri, as well as Phraek Si Racha.

Sourittep Pennaratui is described as the first Siamese king, ascending the throne around 757 CE and serving as the ancestor of Uthong, the founder of the Ayutthaya Kingdom. His reign unfolded during the decline of the Dvaravati polities. Following his time, Chinese sources record continued diplomatic activities from the polity's successor, while later Siamese traditions developed complex genealogical claims linking various dynasties to him. During his reign, Sukhothai, Lavo, and Talung (เมืองตลุง or ตะลุมดอ) were brought under his control.