Tarabya was originally a commoner by the name of Nga Pa-Mun (ငပမွန်, ), or A-Che-Mun (အချဲမွန်, ). His ascent to power was accidental. He was a brother-in-law of Akhamaman (also known as A-Kha-Mun), the self-proclaimed king of Pegu, who successfully revolted against King Narathihapate in 1285 during the Mongol invasions of the country. Two (or three) years later, Akhamaman was assassinated by his brother-in-law Lekkhaya Byu. In response, Ma Ta-Shauk (မတယှောက်), Akhamaman's and A-Che-Mun's father-in-law, recruited A-Che-Mun to eliminate the usurper. Eight days after the death of Akhamaman, A-Che-Mun assassinated Lekkhaya Byu. He declared himself king of Pegu with the title of Tarabya.