For his acting in The Killing Fields, Haing S. Ngor won an Oscar award for Best Supporting Actor.
During his time in America he made books. He wrote an autobiography "Survival in The Killing Fields and A Cambodian Odyssey". 

After coming to the United States he didn't resume his medical practice but he did venture in other activities. He founded the Dr. Haing S. Ngor Foundation which helped raise funds for Cambodian aid.
He also built an elementary school and helped low income families in producing a mill. After his death, his niece took up the position of President of the Foundation. 

Throughout his life, Haing S. Ngor suffered many gruesome sights. He watched his wife die in agonizing pain because she was in labor and needed a C-section.
Performing the duty would have exposed himself as educated and all three of them would have been killed so he watched her life wilt away in anguish.