First attempt to seize power in Cambodia Chaophraya Chakri ascended as
King Rama I in 1782, founding the
Chakri dynasty. Baen had instrumental role in the ascension of the king. Formerly a Cambodian minister, Baen then became a loyal aide of the Siamese king. Meanwhile, in Cambodia, Oknha Kralahom Sous had declared himself
Samdech Chauponhea or Second Chief Minister, second only to the Chauvea Tolaha himself. Uneasy pact between Chauvea Tolaha Mou and Samdech Chauponhea Sous began to crumble. Sous decided to get rid of Tolaha Mou altogether. Sous sent a secret letter to his 'sworn friend' Yomreach Baen at
Bangkok, asking Baen to join him in Cambodia to overthrow the rule of Tolaha Mou. Yomreach Baen told King Rama I of Siam about this secret letter from his friend in Cambodia. The Siamese king saw this as an opportunity to expand Siamese influence into Cambodia. King Rama allowed Baen to bring forces into Cambodia to seize power. Samdech Chauponhea Sous personally waited for Baen at Battambang as escorted Baen to Oudong, where they conspired to overthrow Tolaha Mou the Cambodian Prime Minister. Sous and Baen led forces to capture Tolaha Mou, who fled to Bassac (Ba Thắc, in modern
Sóc Trăng province at the mouth
Bassac River) but the Cambodian governor of Bassac arrested Tolaha Mou and sent him back to
Oudong, where Tolaha Mou was executed in October 1782. Pact of these 'sworn friends' Sous and Baen in Cambodia lasted only for two months until Baen eventually murdered Sous in December 1782, taking all power to himself. Baen declared himself
Chauvea Tolaha or Prime Minister of Cambodia, also allying with Oknha Kralahom Pok the caretaker of young king Ang Eng. The ten-year-old king Ang Eng had been a powerless puppet king since his ascension in 1779 while his powerful ministers vied for power in Cambodia. Oknha Decho Ten, governor of
Kampong Svay and brother of Tolaha Mou, was still standing against Baen at Kampong Svay. When Yomreach Baen sent his forces under Oknha Chakrey Kep to attack Kampong Svay, the
Chams of
Tbong Khmum, under leadership of a Cham official Tuan Set the Cambodian royal capital. In
Bangkok, King Rama I assigned a residence for the Cambodian king Ang Eng at Sanam Kraboe or Buffalo Meadows under his command to join this campaign. Baen was also assigned to bring his Cambodian forces from Battambang to join the main Siamese forces at Bassac (in modern
Sóc Trăng province) to conquer Saigon. However, the campaign ended up with the Siamese defeat by the Tây Sơn in the
Battle of Rạch Gầm-Xoài Mút in January 1785. Aphaiphubet himself could only march to Longvek where he was defeated and pushed back by the Tây Sơn forces.
War with Tây Sơn These Tây Sơn victories allowed the Tây Sơn to exert control over the eastern half of Cambodia, while the western half was under the pro-Siamese agent Chaophraya Aphaiphubet Baen. When the young Cambodian king Ang Eng was staying at
Wang Chao Khamen palace in Bangkok, there was no king in Cambodia. Cambodia was divided into two halves, with the eastern half under the rule of Chauvea Tolaha Ten, formerly Oknha Decho Ten, at Oudong with support from the Tây Sơn and the western half under Chaophraya Aphaiphubet Baen, who also claimed to be
Chauvea Tolaha, at Battambang. There were two Cambodian courts under two Regents of Cambodia with competing claims, each with their own set of
Oknha officials, each in Battambang and in Oudong, each supported by Siam and Tây Sơn. Baen had been in control of Battambang and Northwestern Cambodia since 1783. Cambodian chronicles stated that two Vietnamese Tây Sơn officials named Ong Chor Ma and Ong Thung Binh came to exert power in Cambodia. In 1785, the Tây Sơn sent Oknha Yomreach Koy to attack Battambang. Baen defended Battambang. Oknha Yomreach Koy was shot dead in battle. Conflicts between Tây Sơn leaders
Nguyễn Nhạc and
Nguyễn Huệ weakened Tây Sơn power in
Southern Vietnam. After four years of political refuge and exile in Bangkok, Nguyễn Phúc Ánh brought his fleet to successfully gain foothold in Cochinchina or Southern Vietnam in 1788. Chaophraya Aphaiphubet Baen took this opportunity to make his own moves against his rival, the Tây Sơn-backed Chauvea Tolaha Ten. In 1788, Baen sent his two commanders Oknha Chakrey Kep and Oknha Yomreach Kan to successfully seize Oudong, prompting Chauvea Tolaha Ten to flee to Saigon under protection of
Phạm Văn Tham, the Tây Sơn leader at Saigon. Chakrey Kep and Yomreach Kan pursued Tolaha Ten towards the
Mekong Delta to Saigon. Cambodian and Thai chronicles stated that when Nguyễn Phúc Ánh reached Prek Thleang, Ong Choc Sim (presumably Phạm Văn Tham) came out to attack Nguyễn Phúc Ánh. Oknha Chakrey Kep and Oknha Yomreach Kan led Baen's Cambodian armies to help Nguyễn Phúc Ánh at Prek Thleang, allowing Nguyễn Phúc Ánh to prevail over Phạm Văn Tham. Nguyễn Phúc Ánh captured Saigon in September 1788. Ong Choc Sim or Phạm Văn Tham and Chauvea Tolaha Ten fled from Saigon to Bassac (Ba Thắc). Oknha Chakrey Kep joined Nguyễn Phúc Ánh in their attack on Bassac, resulting in the surrender of Phạm Văn Tham. Eventually, Oknha Chakrey Kep captured Chauvea Tolaha Ten in February 1790. Tolaha Ten and other pro-Tây Sơn Cambodian officials were arrested and brought to Baen at Battambang. Baen executed many of the Tây Sơn-aligned Cambodian officials but chose to spare Tolaha Ten and sent Tolaha Ten to Bangkok, where Ten was again spared by the Siamese King Rama. With the pro-Siamese Chaophraya Aphaiphubet Baen prevailing over the pro-Tây Sơn Chauvea Tolaha Ten in 1790, Cambodia was united under Baen, bringing Cambodia into Siamese influence. == Regent of Cambodia ==