I may be the odd ball here but let me just say, it isn't odd at all that Thap is falling for Fang or will fall for her because there's a thai quote that goes:
"Rak tae pae krai sheat" - basically translated as, "True love is defeated by nearness" which means, even though Thap & Feung were in love, there was a long separation where a lot of things changed. And then, he and Fang had unfinished awkwardness and they got close at times. He must not have noticed that he and Fang had lots of bickering moments where they had chemistry. Is it so wrong that Thap should fall for another female (sister or not) when he's hurt and lonely in a time of war? The man doesn't have 2 years to get over a lost love, 55555 ... What about Feung? We saw her change in behavior towards Khap before the "r-scene". We saw how she cared for Khap. Is she not at fault for the fact that her heart had wavered too?
It all may look very wrong to some of us that Thap should fall for his ex's gf, but it actually happens more often than you think. Especially during those times. If anything, a man in those times would have taken both sisters as his wives.
The back-hug scene that everyone is talking about... I think Thap didn't realize he was feeling jealous towards Fang. To him he was just being his normal protective self. But Fang starts running away from him and telling him not to follow and all that, what does a man do? He chases! That's a man's natural instinct. He feels the resistance in Fang and how she was trying to avoid him. When he was able to grab her the first time and they had a "gaze moment" something must have clicked for Thap because now he feels like he needs to find out what it was. The second "gaze moment" was deliberate because Thap wants to see if the spark was actually there... and that's when he confirms it with a back hug.
Their scene may have been executed awkwardly, but that was my interpretation of it.
