These were turbulent times for the future of Thai King with the Kingdom of Siam. Under invasion continuously from the Burmese. Thong Duang fought alongside his friend Taksin in Ayutthaya. Until in 1767, Ayutthaya was collapsed by the Burmese army who completely destroyed the city. In 1768 Taksin founded a new capital at Thonburi and crowned himself King of Thon Buri. In 1781, While he went on the campaigns against Cambodia. The conflict intensified occur at Thon Buri. The rebels, who want to controlled and seized power of the King Taksin. Causing suffered greatly to the public. He took his troops back to Thon Buri immediately, For suppress the rebels. He saw the cause in the rebellion, . Thus King Taksin was executed by cutting off his head, and ThonBuri period has ended.
Thong Duang has crowned as the King name is "King Ramathibodi Srisinthorn Mahachakriboromnat Phra Phuttha Yodfa " on 10 June 1782 as the first monarch of the Chakri dynasty.