What seems to be the first Vietnamese gay film, check out the wiki page of it here.
Lost in Paradise is a 2011 Vietnamese drama film directed by Vũ Ngọc Đãng. Its original title is Rebellious Hot Boy and the Story of Cười, the Prostitute and the Duck (Hot boy nổi loạn và câu chuyện về thằng Cười, cô gái điếm và con vịt), shortened to Rebellious Hot Boy (Hot boy nổi loạn) or simply Hot Boy. The film is set in Saigon and has two separate story lines. The first depicts a love triangle between three male prostitutes, Lam, Khôi and Đông. The second concerns a mentally-handicapped man, Cười, his friendship with Hạnh, a prostitute, and his attempts to raise a duckling. The film was a strong critical and commercial success in Vietnam. It has been shown at several international festivals, from which it garnered more mixed reviews. In particular its portrayal of homosexuality has been noted as ground breaking within the context of Vietnamese cinema.