Saint Jack (1979) on Netflix

Compelling character study, revolving around Jack Flowers (Ben Gazzara), an American hustler trying to make his fortune in 1970s Singapore in small time pimping. He dreams of building a fortune by running a brothel himself and returning to the States to lead a life of luxury. Savvy but not unsavory he strikes up a friendship with William Leigh (Denholm Elliot), a genial and decent auditor who travels to Singapore every year. Ultimately, the background of the Vietnam War comes into the picture as Jack is offered the opportunity by the CIA to run a brothel for the R&R activities of U.S. soldiers on leave in Singapore.