He came to power by overthrowing King Narapati III in 1551, the culmination of his six-year rebellion (1545–1551) with the support of the Shan state of Mohnyin.
In the 1530s, during the reign of King Thohanbwa of Mohnyin, Sithu Kyawhtin was governor of Salin, a strategic city on the Irrawaddy about 250 km south of Ava (Inwa).
[1] In the following dry season campaign of 1544–45, he was able to retake Salin briefly but his small army of 3000 men was eventually defeated by larger Toungoo forces.
He barely escaped, fleeing west alone by himself to Kale (Kalay), a vassal of Mohnyin,[7] and then to Chin Hills.
The song, ascribed to be composed by Manpau,[10] the grandson of Gophung, in their local language, says as follow: (Free translation): At Mohnyin, Sithu Kyawhtin became a central figure in his thwethauk brother Sawlon II's plan to overthrow King Hkonmaing at Ava.
But Sawlon II along with other chiefs of the Confederation reluctantly agreed to Hkonmaing as the new king of Ava because of the impending Toungoo threat.
[11] However, after successive military defeats that allowed the Toungoo takeover of central Burma to Pagan (Bagan), Sawlon II had enough of Hkonmaing's leadership.
[12] Sithu Kyawhtin's popularity and increasingly independent policies were seen as a threat by his hitherto overlord Sawlon II.
Circa 1548/49,[note 4] Sawlon II marched to Sagaing only to see that his nominal vassal was now in much stronger position.
The two thwethauk brothers met near the Ponnya Shin Pagoda near Sagaing, and amicably worked out the differences.
Facing an existential threat, the Confederation states pledged their full support, sending troops, food and arms in preparation for the invasion from the south.
On 14 June 1553, Bayinnaung sent two 7000-strong armies led by Crown Prince Nanda and Minkhaung II of Toungoo to invade Upper Burma.
Avan defenses, supported by nine Confederation armies from (Bhamo, Kale, Mogaung, Mohnyin, Momeik, Mone, Nyaungshwe, Theinni and Onbaung-Thibaw), could not stop the advance, and the capital Ava fell to the southern forces on 22 January 1555.
[19] Sithu Kyawhtin and his five servants in disguise slipped out of the city, and fled east to join the Onbaung saopha's forces but were captured en route at Mekkhaya.
[21] He was one of four former kings (along with Mobye Narapati of Ava, Mekuti of Lan Na and Maha Chakkraphat of Siam) honored by Bayinnaung at the opening ceremony of the newly rebuilt Kanbawzathadi Palace on 16 March 1568.