He won the Academy Award for Best Supporting Actor for his portrayal of Cambodian-American journalist Dith Pran in the biographical drama film The Killing Fields (1984).

[3] Ngor trained as a gynecologist and obstetrician, practicing in Phnom Penh before the capture of the city by Pol Pot's Khmer Rouge in 1975.

Ngor was expelled from Phnom Penh with the bulk of its two million inhabitants as part of the Khmer Rouge's idea Year Zero and imprisoned in a concentration camp with his wife, Chang My-Huoy, who required a cesarean section and died with the couple's unborn child[1][4] during labor in 1978[3] because it was impossible to perform the surgery without risking the whole family's life.

[9] After the fall of the Khmer Rouge in 1979, Ngor and his niece crawled to safety in a Red Cross refugee camp[9] in Thailand, where he subsequently worked as a physician.

[15] Ngor was not initially interested in the role, but interviews with the filmmakers changed his mind, as he recalled that he promised his wife to tell Cambodia's story to the world.

[14] As part of his humanitarian efforts, Ngor built an elementary school and operated a small sawmill that provided jobs and an income for local families.

[14][18] Three alleged members of the "Oriental Lazy Boyz" street gang, who had prior arrests for snatching purses and jewelry, were charged with the murder.

[7] Prosecutors argued that they killed Ngor because, after handing over his gold Rolex watch willingly, he refused to give them a locket that contained a photo of his late wife, My-Huoy.

Kang Kek Iew, a former Khmer Rouge official on trial in Cambodia, claimed in November 2009 that Ngor was murdered on Pol Pot's orders, but U.S. investigators did not find him credible.