Luang Sawat(2012)

Original title: ลวงสวาท

Detective Petch receives an assignment of investigating a murder case. The only evidence he has is a recording of a woman moaning while having sex. There are 3 suspects; May, a prostitute, Daeng, a hairdresser and Ploy, his own wife. He must have sex with all 3 women in order to find out who's the owner of the voice in the recording.