Soon after the fall of Ayutthaya in 1767, the Burmese shifted the bulk of their military forces northward to engage in the Sino-Burmese War (1765–1769), leaving behind only a small garrison near the ruined capital. In the resulting power vacuum, Siam fractured into five competing local factions, each led by regional warlords. One of Ayutthaya’s former governors, Phraya Tak, who had governed the town of Tak in the northwest, fled east to Chantaburi. There, he regrouped and rallied loyal supporters, eventually raising an army of around 5,000 men. With this force, he launched a bold campaign to drive out the remaining Burmese troops and restore order in the shattered kingdom.

 

Following his military victories, Phraya Tak established a new Siamese capital at Thonburi in December 1767 and crowned himself King Taksin, a name combining his title and personal name, Sin. Strategically located on the west bank of the Chao Phraya River, Thonburi offered strong natural defenses and access to trade routes, making it ideal for both military operations and economic recovery. From this new base, King Taksin launched swift campaigns to reunify the kingdom, defeating various regional rivals. By August 1770, he had successfully reunified Siam in just three years after Ayutthaya’s fall.

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Siam was also engaged in a series of military conflicts with in areas around Burma, Cambodia, Vietnam, and Laos that broke away after the fall of Ayutthaya. In the north, conflict with Burma over control of Lanna culminated in the successful capture of Chiang Mai in 1775, ending two centuries of Burmese dominance there. Siam also successfully defeated the Lao kingdoms, and successfully brought home the revered Emerald Buddha - that was taken away by Laos when they occupied Chiang Mai. 

These campaigns took a toll on King Taksin. It is said that by this time, King Taksin had already started to show signs of mental distress and paranoia. His actions of meeting out severe punishments and executions were seen to be in unwarranted and excessive. In March 1782, a rebellion broke out, which led to the intervention of Phutthayotfa Chulalok - the nation's highest ranking military commander, to take over control. 

Upon his return, he convened a judicial court that placed King Taksin and the rebellion leader on trial for their actions. Both were found guilty of ‘improper and unjust actions that caused great pain for the kingdom’, and were executed together with their conspirators. Phutthayotfa Chulalok thereafter was crowned as the new king.