Surindraraja

Surindrarāja (, ) was an 11th-century Siamese monarch recorded in the Ayutthaya Testimonies as the ruler of Phraek Si Racha. At the age of 15, he succeeded his father, King Srisimha, at Phraek Si Racha circa 1050. Subsequently, he relocated the royal seat northward and established a new capital, which he named Chai Nat.

Surindrarāja was the younger son of Queen Suchāvatīdevī , the principal consort of King Śrīsiṃha. He had three siblings: the eldest, Jyeṣṭhakumāra (เชษฐกุมาร), who was also born to Suchāvatīdevī but died in infancy, and two half-brothers—Sūryavaṃśa and Anurāja —who were born to the secondary queen consort, Suvaṇṇapabbata .

Surindrarāja is said to have ruled for 38 years before dying at the age of 53. He was married to Queen Candradevī , though their union produced no issue. Following his death, the throne was inherited by his half-brother Sūryavaṃśa in 1088. His reign is chiefly remembered for the establishment of Chai Nat as a royal and administrative center, and coincided with Pagan dominance over Suphannaphum in 1081, as well as its subsequent invasion of Xiān at Ayodhya in 1087, which resulted in the death of Ayodhya's king Narai I that same year.

However, the exact location of Chai Nat, to which Surindraraja moved his seat, remains uncertain. It has been suggested that Phitsanulok was known as Chai Nat during the early Ayutthaya period. Phitsanulok had also served as the seat of Surindraraja's line in an earlier period, during the reigns of the brothers Visnuraja and Vijayaraja, with Vijayaraja being Surindraraja's grandfather.