When his father King Theingaba of Toungoo died on 29 March 1367, Pyanchi was in exile at Pegu (Bago) in the Mon-speaking Kingdom of Hanthawaddy.
Though he had been estranged from his father, Pyanchi returned to his native Toungoo (Taungoo), and took over the throne with the royal style of A-Saw Myat-Swa Nawrahta.
With Ava still firming up its borders with its neighboring states in the first half of the 1370s,[note 1] Pyanchi essentially ruled his fiefdom like a sovereign king.
A Toungoo−Prome axis backed by Pegu would form a formidable Lower Burma bulwark against Central Burma-based Ava.
[note 2] At Toungoo, Ma Sein, the commander of the Peguan army stationed there seized the throne, and held out for three months.