Initially a leader of the guerrilla resistance against the colonial French, he went on to become a prominent general in the Khmer National Armed Forces (FANK) during the Cambodian Civil War, as well as a businessman and occasional writer.

[2] In 1949 he joined the Khmer National Liberation Committee, becoming its Supreme Army Chief, then from 1951 he associated himself with the forces of Son Ngoc Thanh in Siem Reap, though he continued to operate as a regional warlord, maintaining his own troops.

[4] After three years' imprisonment, during which he occupied himself by writing a number of well-received romantic novels,[5] Chantaraingsey was released and went on to accrue a large personal fortune through a variety of business ventures, notably after Sihanouk appointed him director of the state-run casino in the capital.

As in his Issarak years, Chantaraingsey ran the province as essentially a personal fiefdom; apart from running a successful pacification program, his purchases of American arms from neighbouring generals made his forces ultimately too powerful for Lon Nol to directly challenge.

Some accounts state he was killed in this area in May while trying to break out to the Thai border,[8] but he was reported to still be alive, and continuing resistance against the Khmer Rouge, in June 1975, at which point he was commanding some 2000 men in the Cardamom Mountains.