This movie is also called "Dust of life" in English and was made by Alex Bouchareb in 1994.
In 1975, 3 kids decide to escape a reeducation camp in the Vietnamese equatorial forest near Cambodia where the Amerasians are imprisoned, tortured both mentally and physically. Son, the hero is sent in that camp after her mother fails to find his father to send him away to America.
Search the web for the title to find more information. You can find the poster of the movie on cineposters dot com.
Kind of reminds me of Papillon or the Killing Fields though maybe a notch down in terms of realization... This movie is based on facts from the after war.