I'm doing a project on Cambodia in school, and I read, "Tomorrow I am Dead" by Bun Yom, where he tells of his experiences as a member of the Cambodian freedom army. However, I cannot find any corroborating sources. Did this exist, and if so, how big of a role did it play in fighting the Khmer Rouge?
He probably means the Khmer Serei (Free Khmer), a US backed anti-communist/anti-monarchist group which had roots in the Khmer Issaraks of the 1940's and 50's. They were mainly involved with fighting Prince Sihanouk's forces, but many were little more than bandits. Some worked with US Special Forces in South Vietnam, and many of these were flown to Phnom Penh in March 1970 to back up the Lon Nol government. Although well-trained they were not a major element in the 1970's civil war.
Some went on after 1979 to form the KPNLF, a group which was in an (often uneasy) alliance with Khmer Rouge fighting the Vietnamese and PRK government.