This is fun! I have poor book/movie memory, so I wouldn't be very good at guessing, but I wanted to participate, too. So, I wanted to add some more lakorn summaries. Granted, some are a bit obvious, but whatevs:
# 1: Nang'ek and Pra'ek have disliked each other from the beginning. The Nang'ek's sister is married to the Pra'ek's brother. The brother and sister won a honeymoon getaway to an island but are unable to attend. The Nang'ek sees this as a great idea because she needs to go to the island for her job. The Pra'ek also see this an a great opportunity to visit his girlfriend, who lives on the island. So, the Nang'ek and Pra'ek are forced pretend they are the newlyweds.
#2: The Nang'ek and Pra'ek are haunted by a spirit of a mysterious woman. Her spirit lives in the ocean and comes out during the night to suck the blood of helpless humans.
#3: The Nang'ek is a talented wedding planner. She is hired to plan the Pra'ek's wedding to his annoying fiance. Predictably, the wedding planner falls in love with her client.
#4: The Nang'ek works for the Pra'ek's "father's" company. One night, in her office, the nang'ek hears the voice of a spirit. The spirit informs her that someone is plotting to kill his brother. The Nang'ek sets out to get the message across.