The Vietnamese Embassy in Italy received the prize on behalf of Khoa, who currently lives in Canada, on Wednesday.
"An interpretation of instinct, energy and dynamism for a character who moves in the chaos and madness of Ho Chi Minh City," the festival stated in a Facebook post Thursday.
He pocketed one of the five most important awards of the night, with the remaining four being best actress, best film, best director and most original film.
Developed from the critically acclaimed short film "4:30 p.m.", screened at Cannes Film Festival in 2013, "Rom" portrays a teenage boy of the same name living in a Saigon slum who buys lottery tickets for people in the neighborhood. His aim is to collect enough money to find his parents, who had abandoned him as a child.
The crime drama pocketed the grand prize at 2019 Busan International Film Festival in South Korea.
The 18th Asian Film Festival screened 28 feature and two short films from 11 economies, including Japan, South Korea and China. Three other Vietnamese movies shown at the event included mega hit ‘Bo Gia’ (Dad, I'm sorry), horror ‘Bac Kim Thang’ (Home Sweet Home), and comedy drama ‘Tiec Trang Mau’ (Blood Moon Party).