In the reign of King Taksin, Relations with foreign countries were as follows:
When Ayutthaya fell to Burma in 1767, Cambodia, a Thai vassal state from Ayutthaya times, asserted its independence. Several expeditions had been sent to take Cambodia. In 1781 the king wanted to categorically annex Cambodia. His wish had not been realized when the reign came to an arrupt end.
Relations between King Taksin and the Ching Dynasty can be divided into three periods according to time and situation:
1767-1770 : The Ching Dynasty refused to accept King Taksin's sovereignty due to a false report from Morsuelun of Bantaimat.
1770-1771 : The Ching Dynasty began to realize that Morsuelun's report was false and began to change its attitude towards King Taksin.
1771-1772 : King Taksin's envoy was warmly received and given special support by the Ching court.
Thai and Vietnamese relations in the Thon Buri period could be divided into two stages. In the first stage Vietnam cultivated friendship with Thailand because it believed the Thais could help settle its internal problems. Later when Thailand had differences with Vietnam regarding Cambodia, relations between the two countries became so strained towards the end of the reign that they almost came to war.
Nakhon Si Thammarat
After taking Nakhon Si Thammarat in 1769, King Taksin gave the administration back to the local authorities. He raised it to the status of a vassal state. Its governor held the rank of Chao Nakhon Si Thammarat, the equivalent of a king. The vassal state and Thon Buri were on very good terms throughout the reign.
During the first ten years of the Thon Buri period, Thailand and Burma were at war eight times. It can be said that Burma was Thon Buri sworn enemy.
Major Malay provinces, namely Pattani, Sai Buri, Peris, Kelantan, and Trengganu had been Thai vassal states since the days of Sukhothai. When Ayutthaya fell, these states became independent. As King Taksin was occupied with the war against Burma and the revival of the country, the Malay states were left free from Thai influence until the end of the reign.
Major Lanna states, namely Chiang Mai, Lampang, Lamphun, Phrae, and Nan, governed themselves with their own princes. They were important strategically for both Thailand and Burma that the two nations vied for control these territories since Ayutthaya times.
At the time, Laos consisted of three states :- Luang Phrabang, Vientiane, and Champsak. King Taksin exerted his influence over Laos twice. Troops were sent in 1776 to take Champasak, Khong and Attapeu. It also succeeded in persuading Cambodian jungle towns of Talung, Surin, Sangkla, and Khukhan to acknowledge Thai sovereignty. Thus the whole of southern Laos came under Thai influence. A second expedition was sent in 1778 to take Vientiane. The Emerald Buddha and the Phra Bang were brought to Thon Buri. Luang Phrabang, which had conflicts with Vientiane, also pledged loyalty to the Thai monarch. Laos, therefore, became a Thai vassal state until the end of the reign.