This was the worst possible ending for the series and I am so disappointed.
I was okay with the final episodes 7 and 13, they redeemed at least some of the fuck ups of earlier episodes. It could have been a nice basis for the special epsiode, but they totally screwed it up.

I honestly expected the special epsiode to give us a glimpse of their lives together after all the drama, their evolving relationships, their future plans etc. Instead the special epsiode focuses just on Payu and Prapai being too desireable for their own good. That itself is not the main problem, Rain and Sky being insecure and unsure in their relationships could have been a nice storyline, with Payu and Prapai reassuring their boyfriends.
But no, the insecurity-problem is brushed over with Rain putting Payu in a costume and Sky and Prapai screwing in a bath tub...wow. It was so difficult to watch, because it's so UNBELIEVABLY CRINGEY and also a lot OOC in my opinion.
That's also the reason why their acting was not as good in this episode, it feels like the actors didn't feel comfortable at all with this storyline.
Also, Payu is a gigantic asshole to Rain and I absolutely hated it.

I regret watching this clown show of an epsiode, I'm just gonna pretend it doesn't exist...