I'm gonna assumed people rate with a low score this movie because they expected this to be a horror movie or a romantic one... This isn't romantic neither horror, this is a psychologic film!

[spoiler] For those who don't know "The Blue Hour" makes a reference to the time between day and night, dream and reality, good and evil so in order to fully understand the story you need to know that.
This is my opinion and I've read some viewers tought the same; Phum's actually an alter ego created by Tam's mind, if you think straight, there isn't too much background from Phum's life, all we know is that he escape from home and in one scene when they get their first encounter you will notice Phum says Tam looks more good looking in person and when they were kissing Phum says he don't knew Tam likes that kind of stuff, knowing this I could understand he wasn't real, first because when the bullies stole Tam's phone they didn't found any message from Phum, after this everything makes sense, Phum say that beceause he was on Tam's mind but that was the first time he was actually seeing him on the outside and didn't know Tam likes some things because of his personality, always shy and unconfident but founds himself finally in peace to be who he really is.
The second half of the movie becomes darker and this is when most viewers don't understand anything, so the whole scenes in the pool represents Tam's mind, messy, abandoned and with dirty water and that's the place where Phum comes so thats why he always get Tam to that place; the dumpster represent Tam's life from his perspective, methaphorically he could be a beautiful land full of life but instead is full of garbage, darkness and death. In order to get the life he wants he takes de decisiton to kill his family (The scene with the gangters is actually him taking that decision) and at the end he finds peace, the river represents his mind after all of this. [/spoiler]

Oabnithi was nominated to the Thailand National Film Association Awards for Best Supporting Actor and no doubt he did a great job on this, hopefully now he's getting the recognition he deserves, Gun Atthaphan did wonderful too.

So don't get affected by the score, this is one of those movies that deserves a rewatch.