Straight copy of Fatal Attraction, with a couple of small add-ons.
Pei and Sunny run a car dealership. Sunny is a bragging womanizer, who keeps the underwear of his conquests filed in a briefcase. Pei is a conservative and very happily married man. Pei meets Lu, a single psych graduate, at a party. Pei's wife Winnie goes to KL to a wedding, and Pei is drawn into Lu's clutches. They fool around happily while the cat's away.
Winnie returns, Pei wants to end things, but Lu won't let him go. Lu tries increasingly trickier tactics to keep him, including latching him into a chastity belt while sleeping, befriending his wife and kidnapping his cute daughter. And things get worse.....