The Rattanakosin Kingdom was the fourth Thai Kingdom, after the Sukhothai, Ayutthaya and Thonburi Kingdoms that preceded it. When the powerful Ayutthaya Kingdom was destroyed and burnt down by Burmese armies in 1767, a small period of chaos and Burmese occupation ensued in the lands of Siam. The resistance was led by General Taksin, a capable military leader who defeated the Burmese within one year and established the new Siamese capital in Thonburi, right across the Chao Phraya River from Rattanakosin. Instead of just re-conquering Siam, he also seized Western Cambodia, Terengganu state in Malaysia , Lanna (modernNorthern Thailand) and Laos.
Despite these successes, in 1779 King Taksin proclaimed himself a sotapanna (or divine figure), in opposition to the powerful position of Buddhist monks. The state was in economic turmoil, with rampant corruption and famine. Many Chinese factions were discontent with the current leadership and King Taksin tried to restore order by harsh punishments and purges. While he was away, a rebellion forced King Taksin to step down and he was secretly executed.
When Phraya Chakri, a popular general under King Taksin who had successfully managed the invasion of Cambodia, returned, he was offered the throne. He was crowned King Rama I, the first King of the Chakri dynasty that started the Rattanakosin Period.
One of his first actions was to move the capital across the river, from Thonburi to Rattanakosin.
According to him, Rattanakosin had a more strategic location, as he turned it into an artificial island with the the Chao Phraya River in the west and man-made canals in the east.
Previously, Chinese merchants had occupied Rattanakosin, but they were now relocated outside of the new city walls.
King Rama I restored the social and political system of the Ayutthaya Period, even imitating that city's layout and architecture in Rattanakosin. For example, the Grand Palace's building plan closely resembled that of the Grand Palace in Ayutthaya. Even the bricks from the ruins in Ayutthaya were moved downstream to be incorporated into the new capital's grand scheme.