I think, for some woman, that forcing a kiss on her is not a way to express his emotions...it seems more like they're trying to mark their territory. I'm not saying that was the case for Prajak, but for someone like Wanida, it could be like in the caveman days where the guy just clubs the woman on the head and drags her to his cave and she is automatically his. I think for Wanida, she is a woman who doesn't need actions, because people have done so much to her already...and especially in her grandma's case, she needs some honesty. She never asked for Prajak to do anything for her, all she has ever wanted was honesty, from her dad, Prajak, the Mahasak family. She's a woman who wants answers, and not just actions like that. I think they're just on the wrong page, Prajak thinking that Wanida will just know how he feels from a forced kiss, and Wanida who genuinely wants to hear the truth from Prajak. Because he is a man who says one thing and does another, like how he claims to know the kind of woman she is, but then when a man comes into the picture, he degrades her. He never told her he had feelings for her, so she could never know that he was jealous...so in that moment, that kiss seemed more like, "You're my woman" type of kiss than an "I"m falling in love with you."
I was someone who thought Prajak did love Pisamai at one point, and then literally someone better came along, and instead of letting her go, it seems he keeping her around in case things don't work out with Wanida. I don't see having her around is some kind of responsibility he has to her, I think he just wants that safety net. But I do feel that Prajak is definitely torn by a lot of things, especially supposedly being a man of honor...he wants to do right by his family, and wait until his debt can be paid off, but at the same time, he feels that he needs to be a good husband to his good wife. He's being torn in all sorts of direction, from his mom, Dao, Pisamai...the only one not making him do anything is Wanida, and he doesn't even know how to deal with it. He treats her the way he would any other person, by not showing weakness to her, even though he's completely putty in her hands.
I love discussions like this
I think Pisamai was doing a good job in hiding her true character, and I do believe she was always bad...some people will never show who they really are until they are faced with situations to bring those certain characteristics out...and you can either choose to do the right thing or the wrong thing...and she chose the wrong thing. It's like what we learn in Biology, we inherit genes from our parents, that sometimes don't come to the surface until later, but those genes are still there...there just needs to be something to bring it out. She thought she had a cozy life already, but she's just like a kid who didn't get her way. No one told her what's she's doing is wrong, so she will continue to act that way until someone stops her.