Taksin's reunification of Siam

Following the Sack of Ayutthaya and the collapse of the Ayutthaya Kingdom (1351–1767) during the Burmese–Siamese War (1765–1767), a power vacuum left Siam divided into 5 autonomous cliques (self-proclaimed kingdoms)—Phimai, Phitsanulok, Sawangkhaburi, Nakhon Si Thammarat, and Thonburi. The Burmese invasion force, having returned to Burma off their successful sack of Ayutthaya and to defend its homeland against an imposing Chinese invasion of Ava, were too preoccupied to take advantage of the power vacuum in Siam.

Source: Wikipedia — Taksin's reunification of Siam (CC BY-SA 4.0)