The two-times-great-grandson of King Sithu II founded Toungoo near the end of the Pagan Empire in 1279.
According to the regional chronicle Toungoo Yazawin, he was born in Pyu where his father had been placed under house arrest since 1256 by a rival governor from a Mon state to the south,[1] which most likely was Pegu (Bago).
[note 1] The fight between the rival governors took place during a brief interregnum following the death of King Uzana of Pagan (Bagan) c. May 1256.
At the capital Pagan (Bagan), a power struggle broke out between Crown Prince Thihathu and his half-brother Narathihapate.
[5] He also brought in Kayin Ba, a commoner from the nearby Htihlaing village, into his inner circle, appointing him chief of law enforcement.
Although Thihathu managed to send an army led by Crown Prince Uzana to retake Toungoo, Thawun Nge quickly submitted to the Pinya forces, and got to keep the governorship.