Siddhijaya Brahmadeva

Siddhijaya Brahmadeva (Thai: สิทธิไชยพรหมเทพ) is described in legend as a ruler of Nakhon Chai Si, which has been identified with the present-day Nakhon Pathom, functioning as the center of Kamalanka. According to tradition, Siddhijaya consolidated authority in the region by suppressing a group of Brahmans, potentially led by Kakabhadra, who had exercised power over local settlements before Siddhijaya's arrival.

Chronological discrepancies within the sources place Siddhijaya's reign in apparent overlap with that of another monarch of Nakhon Chai Si, Kakabhadra. Some scholars have therefore sought to equate the two figures. Nevertheless, the accounts provide grounds for distinguishing them: the legend records Siddhijaya as having come from Manohana and founded Nakhon Chai Si in 590 CE, whereas the Northern Chronicle describes Kakabhadra as ruling Takkasila (another appellation for Nakhon Pathom) for 72 years before he died in 641; thus his reign was 569 to 641, and his grandsons are said to have been descendants of King Tona Brahmin. This suggests a period of political overlap between the two monarchs within the same polity.

During the Sui period (581–618), the Tongdian records the existence of the Tou-he Kingdom, identified with Dvaravati, which was centered at Nakhon Pathom and ruled by a monarch referred to as Pu-xie-qi-yao of the Tou-he-luo dynasty. The relationship between this figure and the contemporaneous Dvaravati monarchs, including Siddhijaya and Kakabhadra, remains unestablished. It was during this period, approximately between 605 and 616, that Dvaravati is first recorded as having sent tribute to the Chinese court.