Just some general commentary as a U.S. viewer watching this movie: It's beautifully directed. I can't comment much on the writing, but as a gay viewer in particular, I really appreciate that the script interweaves two stories: coming out and the coherence of family in a time of grief. The reason I appreciate this is that, even in the U.S., when movies deal with homosexuality, it is generally treated as a singular issue that is separate and distinct from all others. In reality it is one part of the fabric of family and love that comprises everyone's life. Without this key insight, I think the movie would deal with the issue in too patronizing or shallow a manner, as many gay-themed movies do.
Prior to watching I was acutely aware of the commentary that the movie is overlong and not focused enough. There is some truth to this; it is a very long movie for its subject matter. But I think the movie's main strength is in its characters and central subject matter. With too much editing, I could easily see how the core of the movie would be lost. For me personally I was glad the director erred in favor of too much immersion in the interplay between his characters.
As to acting -- clearly I don't speak or understand Thai. But I think some things are universal, like the mother's strength and resolve in times of crisis. And of course Mew's smile. The connection is there.
I loved the movie and I hope it finds its way to broader distribution. If nothing else, the soundtrack should -- it's truly great.
Cheers!