Elephant White (2011) on Netflix

Plot summary

Curtie Church is an American assassin working in Bangkok. He kills a group of captors from the Chang Cao gang and makes it look like the work of the Jong Ang gang, and a fourteen-year-old prostitute named Mae sees him do it. Rajahdon, the client who paid him, had a daughter murdered by traffickers, and now offers a second contract, aimed at the man who runs them. Church turns to Jimmy, an English arms dealer, and rents heavy weapons, intending to set the city's gangs fighting each other so the traffickers destroy one another. He keeps a hideout near a monastery, across from a Jong Ang club, and Mae turns up there while he is eating.