Indaprasthanagara

Indapraṣṭhanagara (Thai: อินทปรัษฐ์นคร) is an ancient toponym attested in several textual traditions of the Tai-speaking people, including the Ayutthaya Testimonies, the Chronicle of the Padumasūriyavaṃśa the Legend of Nakhon Si Thammarat, the Lan Na Yonok Chronicle, the Laotian Phra That Phanom Chronicle, the Legend of Phaya Khan Khak of Isan people. and the Lan Xang Chronicle. These sources collectively place the city's historical memory between approximately the late 4th century and the early 14th century CE, after which Indaprasthanagara disappears from the record following the rise of the Sukhothai and Ayutthaya kingdoms. Although earlier Thai scholarship long equated Indapraṣṭhanagara with the Angkorian Yaśodharapura, closer chronological and contextual analysis suggests that this identification is problematic, as the existence of Indapraṣṭhanagara predates the establishment of Yaśodharapura by approximately five centuries.

The earliest narratives referring to Indapraṣṭhanagara retrospectively place its existence in the 4th century CE, within what is conventionally termed the Proto–Dvaravati period, most notably in traditions associated with King Phrom the Great. Later chronicles further associate the city with the Padumasūriyavaṃśa lineage and with rulers bearing the regnal name Sri Dharmasokaraja I, whose political activities linked central mainland regions with the upper Malay Peninsula. These accounts indicate that Indapraṣṭhanagara functioned as a regional polity of considerable importance prior to the consolidation of Angkorian power and the emergence of Sukhothai.

The reinterpretations founded that Indapraṣṭhanagara was not at Angkor but in the Phraek Si Racha historical region, east of Sankhaburi, as stated in the Ayutthaya Testimonies. This reassessment has significant implications for understanding dynastic relationships, inter-polity conflicts, and alliances among Sukhothai, Lavo, Angkor, and related polities in the 11th–12th centuries, as well as for re-evaluating traditional narratives preserved in later Thai chronicles.