Rather than writing what went wrong in this drama, it is faster to write what went right. Because it will not be long.

Summer is a time of love - what is better than a short summer love story in a beautiful resort?
Clear blue water and amazing beaches would give us really nice background for romance.
Romance that takes place between a popular duo of Boun and Prem who play debt collector and resort owner.
Sound fun?
It's not...
There are 6 episodes in total - each 43 minutes long but in fact only have about 25 minutes of actual drama. Yes, about 20 minutes in each episode is for full intro and ost song, previous episodes summary, and BTS.
But the intro song is really catchy and BTS bits are sometimes funnier than actual drama.

That is all for the positive aspects of this drama if you want to know why - it has the same screenwriter as That's My Candy, plot and story is a mess it has 4 couple in total but not enough time to develop even one of them while plot progression is almost no existent.
The last episode is definitely the best and kinda improves the overall quality of the show. Happy ending - if we get there in a more reasonable way it would be a pretty nice and original drama. But most of the plot goes straight from point A to point D leaving viewers with the feeling that we skipped development in between (That doesn't exist)
Script, storytelling and editing are just painful to watch - I am sure that if I give character and story setting to a group of middle schoolers they would come out with something better than what we get from "professionals" who got paid for this job.

I scored this drama 5,5, only due to my sympathy for the actors. They worked very hard only to star in this flop so the best thing you can do is pretend this drama doesn't exist.