The Sin (2004)

Dhep (Andy-Watchra Thungkaprasert) is a traveling photographer on his way home to broach unresolved problems between his father and himself. But, on his way home to the island, he meets Riam (Helen Nima) at the pier, and swiftly falls in love with her – before learning that she’s his father, Cheng’s (Sorapong Chatree), new wife. Dhep’s stay at their place familiarizes him with the problems between his violent and sadistic father and stepmother, so he tries to treat Riam kindly to make her feel better. But the forbidden love rears its head again, and the pair decides to make a go of it.