Thissa hasn't been promoted as much as the others and she's been with them for like 10 years. Also she's been in crappy lakorns so there a not much coaching there. Even if her acting isn't up to par, I still love her tremendously because she has really good personality. Never has any problems with anyone.
Thisa is like Baifern, ch 7 gives her crappy lakorn for many years. So some don't even know she exist until this lakorn. Her acting is better because she's working with good production and Weir probably help coach her. Sometimes all it takes for an actor to do well is to work with good director and actor. Ch 7 should give her more good roles instead of giving everything to Pooklook. No offense to Pooklook's fans but I think she's not that great of an actress.
I think the leads's development is good. They're opening up to each other a lot and letting their guards down. I think that Naboon likes Rattawan from the start too because he's just too nice to her. We start to see him develop more feelings for her because he's worried about her and always protecting her. With Naboon being nice and sweet of course Rattawan cant help but fall for him.
The romantic and fin scenes are normal and typical for Thai lakorn. There's nothing wrong with it. Like in Bloop Phaeh Saniwatt, pek and nek are always falling into each other for whatever reason. The purpose is to make fans fin.