King Sisowath was born on Sept. 7, 1840; son of King Ang Duong; half-brother of King Norodom and prince Si Votha.
He was a figurehead for the French colonial administration, which had secured the protectorate over Cambodia in a treaty signed by his half brother, King Norodom, in 1863.
Like King Norodom, Prince Sisowath received his education under the surveillance of the Thai sovereign in Bangkok because Siam (Thailand), with Vietnam, had long held Cambodia as their vassalage and chosen Cambodian sovereign. Prince Sisowath remained in Bangkok until his father, King Ang Duong, died in 1860; he then went to Oudong, Khmer's court, to prevent his other half brother, Si Votha from seizing the throne. He forced Si Votha out of Oudong, but the Thais recalled him to Bangkok and hastily installed the more compliant Norodom on the throne.
When the French won partial control of Vietnam in 1862, they claimed a protectorate over Cambodia as well. King Norodom was crowned in 1864 with French consent, and Prince Sisowath withdrew to Saigon, where he was subsidized by the French, who could threaten King Norodom with the prospect of installing Prince Sisowath in his place.
Prince Sisowath remained in Saigon until 1867, when he was called to quell anti-French uprising in Cambodia. He thereafter remained in Phnom Penh and gave his support to the French colonial regime. King Norodom died in 1904, and Prince Sisowath succeeded to the throne.
King Sisowath died in 1927 in Phnom Penh. He was succeeded by his son, Prince Sisowath Monivong.