In America, Dr. Ngor continued to help refugees at the Chinatown Service Center in Los Angeles, where a chance meeting between Dr. Ngor and the casting director for "The Killing Fields" led to a screen test and eventually the role of Dith Pran in the film.
赴美後，吳漢在洛杉磯華埠服務中心擔任輔導中南半島難民的工作。三年後，「殺戮戰場」負責選角的人員在一次宴會中發現吳漢，邀他前往試鏡。他輕而易舉地得到這個演出機會，影片完成後，各種獎座也接踵而來。