Thon Buri (Thai: ธนบุรี) was the capital of Siam (now Thailand) for a short time during the reign of King Taksin the Great, after the ruin of capital Ayutthaya by the Konbaung (Burmese). King Rama I relocated the capital to Bangkok on the other side of the Chao Phraya River in 1782. Thon Buri stayed an independent town and province, and was merged into Bangkok in 1792.
In 1767, after dominating southeast Asia for almost 400 years, the Ayutthaya kingdom was destroyed. The royal palace and the city were burnt to the ground. The territory was occupied by the Burmese army and local leaders declared themselves overlords including the lords of Sakwangburi, Pimai, Chanthaburi, and Nakhon Si Thammarat. Chao Tak, a nobleman of Chinese descent and a capable military leader, proceeded to make himself a lord by right of conquest, beginning with the legendary sack of Chanthaburi. Based at Chanthaburi, Chao Tak raised troops and resources, and sent a fleet up the Chao Phraya to take the fort of Thonburi. In the same year, Chao Tak was able to retake Ayutthaya from the Burmese only seven months after the fall of the city.
Ayutthaya, the centre of Siamese authority for hundreds of years, was so devastated that it could not be used as a government centre. Tak founded the new city of Thonburi Sri Mahasamut on the west bank of Chao Phraya river. The construction took place for about a year and Tak crowned himself in late 1768 as King Sanpet but he was known to people as King Taksin – a combination of his title and personal name. Taksin crowned himself as a King of Ayutthaya to signify the continuation to ancient glories.
In 1782 Thonburi sent a huge army to subjugate nearby kingdoms such as Cambodia and Lao principalities again, but while they were away, a rebellion led by a powerful official broke out. The rebels eventually controlled the capital, forcing the king to step down. It is said that Taksin was allowed to be a monk. Later, the general, Phraya Chakri, the commander-in-chief of the army in Cambodia, who had wide popular support among officials, was offered the throne to King Taksin's commander in chief as he marched back from Cambodia and officially deposed king Taksin from monkhood. Taksin was secretly executed shortly after.
After the execution, the commander in chief assumed the throne of Thonburi kingdom as King Ramathibodi or Rama I. King Rama I removed his royal seat across the Chao Phraya river to the village of Bang-Koh (meaning "place of the island") which he had built. The new capital [of Thailand] was established in 1782, named Rattanakosin. Thon Buri remained an independent town and province, until it was merged into Bangkok in 1971.