After the Fall of the Ming dynasty, a Cantonese named Mo Jiu or Mạc Cửu (鄚玖) migrated from Leizhou, Guangdong Province[1] to settle in the Cambodian coastal port town of Bantaey Meas (Khmer:បន្ទាយមាស) or modern Hà Tiên in 1671.

In 1714, King Ang Tham or Thommo Reachea of Cambodia was driven off by Kaev Hua, who was supported by the Vietnamese Nguyen Lord.

Ang Tham, who had spent about two decades in Ayutthaya, finally returned to Cambodia and reclaimed the throne for himself in 1737, prompting the pro-Vietnamese Satha to flee to Vietnam.

[1] Ang Ton was defeated and took refuge in Hà Tiên under the protection of Mạc Thiên Tứ (known as Neak Preah Sotoat[1] in Cambodian chronicles).

[1] Mạc Thiên Tứ then gained the permission from the Nguyen Lord Nguyễn Phúc Khoát to install Ang Ton as the new king of Cambodia.

The Vietnamese settled on the new territories of the Mekong Delta and maintained military garrisons at Long Hồ, Sa Đéc and Châu Đốc.

[1] During the Late Ayutthaya Period, the Teochew Chinese people from Guangdong Province had migrated overseas to settle in the eastern Siamese coastal port towns,[4] most notably in Bang Plasoi and Chanthaburi.

After Phraya Tak had enthroned himself as King Taksin in December 1767, he sent his diplomatic envoy to Guangzhou in August 1768 to request for the imperial recognition[5][6] in order to secure his relative legitimacy over other rival regimes and lucrative trade with the Chinese court under the tally system.

Mạc Thiên Tứ sent his delegate in a competing mission to Guangzhou, informing the Chinese court that the Ayutthayan princes, the scions of the fallen Ban Phlu Luang dynasty, had been with him in Hà Tiên.

[5][6] The Beijing court refused to recognize Taksin as ruler of Siam in the Chinese tributary system because of the existence of the Ayutthayan princes.

Anuchit Racha explained to King Taksin that, due to the rumors, he was obliged to retreat in order to return to prevent the Thonburi city from descending into upheavals.

When the royal fleet reached Chanthaburi, the king stayed there, ordering Chen Lian and Yang Jinzong to proceed to Kampong Som.

The king also ordered Phraya Phichai Aisawan Yang Jinzong to write a letter to Mạc Thiên Tứ, urging him either to fight or surrender.

Ang Ton, along with his family and the Siamese Prince Sisang, then decided to embark on boats to take refuge downstream at Trolong Khoas[1] near Ba Phnum.

King Ang Ton proceeded from Trolong Khoas to Baria (modern Châu Thành)[1] to be under Vietnamese protection, while the Cambodian common people fortified themselves with the support of Oknha Yumreach Tol near Ba Phnum in defense against the invading Siamese.

Going through dense forests of Cambodia, Taksin finally reached Phnom Penh on November 27, where he was told by Chaophraya Chakri Mud that Oudong had fallen to the Siamese and Ang Ton had fled to Ba Phnum.

He granted[8] ammunitions and rice supplies to Chen Lian at Hà Tiên and to Ang Non at Oudong in order to maintain Siamese position in Cambodia.

King Taksin left Hà Tiên on December 24, 1771[8] along with some members of the Mạc family and other political captives including Prince Chui and Pu Lan the former governor of Chanthaburi.

[1] Nguyễn Cửu Đàm sent the Cambodian commander Oknha Yumreach Tol to lead the vanguard of 10,000 men to attack Chaophraya Chakri at Peam Panca Peas (in modern Prey Veng).

[1] Chaophraya Chakri Mud was defeated and Oknha Yumreach Tol seized Phnom Penh, prompting the pro-Siamese Ang Non to flee to Kampot.

Next year, in February 1773, Nguyễn Phúc Thuần ordered Mạc Thiên Tứ to send a mission to Taksin to seek for peace.

Despite the fact that King Taksin had waged war against the Nguyễn Lords he gave refuge and shelter to some Vietnamese refugees during the Tây Sơn Rebellion, primarily Nguyễn-loyalist mandarins and generals.

One of these refugees was Mạc Thiên Tứ, the former governor of Hà Tiên,[13] who was awarded the Siamese rank and title of Phraya Rachasethi Yuan.

King Taksin, upon learning about the Tây Sơn uprising, sent his delegate to meet with Mạc Thiên Tứ in Cochinchina, suggesting his former enemy to take safety refuge in Thonburi.

In 1780, Preah Ang Keav, the Cambodian delegate, informed King Taksin about a letter from Nguyễn Ánh, the new Nguyen Lord who had been in Saigon resisting the Tây Sơn, to Tôn Thất Xuân telling him to insurrect and seize control of Thonburi.

It is uncertain, but King Taksin's ultimate goal may have been to place his son, Prince Intarapitak, on the Cambodian throne, effectively annexing Cambodia to Siam.

[17][18][19][20] After the destruction Hà Tiên of at the hands of the Siamese and the deaths of Ayutthayan princes, the Qing court of Beijing took an improved attitude towards Taksin.

In 1777, Li Shiyao, the viceroy of Liangguang, expressed his opinion to Emperor Qianlong that Taksin was a formidable opponent of Burma,[6] which was an enemy of China.

In July 1777, Taksin sent three delegates to Yang Jingsu, the new viceroy of Liangguang, expressing his wish to offer tributes to China according to the usual ceremonial practices.

Next year, in 1778, Taksin sent a letter to the Qing court requesting to postpone sending tributes because Siam was suffering from the impact of the Burmese Invasions[6] of 1775-1776.