Taksin was king of Siam from 1767 to 1782. He established his court at the city of Thonburi after the sacking of Ayuthaya by Burma in 1767.
Taksin was in many ways an upstart. He was the son of a Chinese merchant and a Siamese mother who had been adopted by a noble family and raised in the capital. His real name was Sin, but by the time of the Burmese invasion he was governor of the city of Tak. Any governor was known by a title, in this case Phraya Tak, but to distinguish him from his predecessor he was called Phraya Tak Sin, or Taksin.
In fact, Siamese did not have family names until 1916 when they were assigned surnames by Rama VI as a "civilizing" (read: Europeanizing) gesture. Before this, people were known by given name and title, if they had one: hence Taksin.
Taksin was a brilliant military tactician and strategist, but he must also have been charismatic, for he convinced people to follow him. He probably claimed that he was a man of merit, one whose karma was sufficient to allow him to lead. After establishing a solid base at Thonburi, he worked at reuniting the kingdom, which he did quite well, particularly with the help of his general and eventual successor, Chakri.
However, towards the end of his reign Taksin began to act rather erratically. He devoted himself to religious excesses, and required people recognize him as a Buddhist deity close to enlightenment. He had anyone who refused to bow down before him demoted, flogged, and imprisoned.
This is shocking behaviour in a Buddhist kingdom. In modern day Thailand even the king, before whom all other people bow, will kneel down before a monk.
Taksin's paranoid behaviour deteriorated further, and he had anyone who he thought might have committed a crime against him tortured and jailed. Eventually a rebellion was mounted against Taksin by disaffected farmers and provincial officials. As custom dictated, Taksin was killed in the manner fitting royalty: he was placed in a velvet sack and struck on the back of the neck with a sandalwood club. Chakri was invited to the throne, and accepted. He moved the capital across the Chao Phraya river to Bangkok, and a new era in Siamese history began.