Sorry, I just wanted to jump in really quick — I don't think anyone dropped the word "pedophilia"? Unless I'm missing something. If you're looking for a specific term, it seems to be Ephebophilia, which is the attraction to "mid-to-late adolescents, generally ages 15 to 19"; however, it seems to only be sexual attraction, which, because Irin and Namcha's relationship was not sexual in nature, none of these terms apply. Additionally, because Win is a full-adult in real life, and doesn't look like a highschooler (if you see if high school pictures, he looks vastly different from how he looks now), I don't think its true to the scenario to call Irin any of these titles.
However, even if the age of consent in Thailand is 15, Namcha is still a minor. The fact that he is 17 and dating a 24-year-old is mildly concerning, especially when you factor in the fact that they're neighbors and she's been around him his whole life. Honestly, if the flashbacks were just about Namcha's crush on his neighbor, and then they got together when they were adults, it wouldn't be so uncomfortable. I honestly really like age-gap dramas, it's just the minor/adult relationship that makes me not ship them.
I also think that Irin did think they're relationship was genuine, that's why she felt it was necessary to hide it. She didn't want people to know she was dating a highschooler, because it wouldn't be socially accepted. That, in itself, says that this shouldn't be a relationship people support.
I'm still rooting for Inn! I hope that he can help her heal her heart, and that Irin can find happiness elsewhere (and that the sisters can stop fighting over a boy who acts like a dog all the time? Honestly annoying).
Anyways, I hope that cleared some of that up!