I don't really feel like writing a summary for this movie, so I'm going to paste the one from Wikipedia with a few of my added detail because it pretty much sums of the plot of the movie in a few sentences.
Summary
In Thailand, young Ton Chatree (Trairat) is sent to a boarding school by his father to get good grades and not tell his mother about his father about him having a affair. Once in the school, Ton feels like an outcast and misses his family and friends. His new schoolmates tell ghost stories about a boy who died in the school swimming pool and a young pregnant woman who committed suicide. The stories frighten him, thereby exacerbating Ton's difficulties adjusting to the school. However, Ton becomes close friends with another lonely boy, Vichien (Chienthaworn), who Ton later discovers is the boy who drowned, and his death repeats every night. Ton finds a way to help his friend rest in peace by seeking help from the school "weirdo", who tells him that the ghost can not move on till another ghost breaks the cycle. Ton is found later on the floor, apparently, taken some kind of liquid that would just knock him out but not kill him. I'm not sure what the liquid was because my version of the movie did not have English subtitles over the bottle to translate the Thai writing. The boys move Ton's body over to the pool and wait. The scene flashes back to Vichien's death, only this time Ton is there to save him. The scene changes once again and now Ton and Vichien are walking down a road together talking about a girl. Ton gets ahead of Vichien while walking and looks back to hear Vichien say he has to go now. Ton wakes up in the present with the group of boys around him and Miss Pranee running to him.
At the same time, Ms. Pranee (Sukapatana), the school administrator, is deeply troubled by Vichien's death because she believes incorrectly that Vichien committed suicide and that it was partly her fault. At the end of the movie, Ton tells Pranee the truth, that Vichien's death was an accident and that Pranee should not blame herself. Ton and the boys that bullied him and told him the ghost stories are now friends and the troubles between Ton and his dad are resolved.
Vichien's Death And Why He Can't Move On
The wiki summary doesn't go into detail on Vichien's death so I'll explain it for you. The boys of the school were swimming all day. Another boy, jokingly begins to call for help and bob in and out of the water yelling. All the boys that were not in the pool quickly jump in to aid the falsely drowning boy. The students become distressed when they can not find the 'drowning' boy after he goes under water. After a few seconds he pops back up and begins laughing about how scared everyone became. The students slash him with water and say that it's almost 6 o'clock, dinner time. As everyone gets out of the pool Vichien remains and starts to call for help. The other students believe that he is joking and stand around the pool as Vichien is drowning. Hungary, the boys leave the pool for dinner. Vichien goes under the water and doesn't come back up. Hours later at bedtime one of the boys comes to Miss Pranee's office to inform her that Vichien has not returned to the dorm. Miss Pranee imediately rushes to the pool where she finds Vichien's body floating in the water.
The part that really bugs me about this film in the fact that no one but Miss Pranee felt bad in anyway for Vichien. Miss Pranee had nothing to do with Vitchien dieing, but all the students that sat by and watched did and yet they felt no remorse for what they did. They even made of a ghost story about him, saying that he killed himself. Granted that most of the boys that were at the school with Ton arrived were almost as new as he was, but there were a few that had been there when Vichien died.
According to some web searches that I did Vichien couldn't move on to the after life because the Thai people believe that if someone dies in usually ways that are not of natural causes, such as drowning, they wouldn't be able to move on till the cycle is broken.
Review
Thai horror film Dek Hor, or Dorm/ My School, seemed more like a suspense and thriller than horror to me. I wasn't scared during the whole movie. I enjoyed it quite a bit but there were some moments that bored me. It a good suspense film. I would recommend it to anyone.
Watch Online{Click}
Subtitles: English
Video Quality: Fair- Medium
Source: Youtube
I don't really feel like writing a summary for this movie, so I'm going to paste the one from Wikipedia with a few of my added detail because it pretty much sums of the plot of the movie in a few sentences. 
At the same time, Ms. Pranee (Sukapatana), the school administrator, is deeply troubled by Vichien's death because she believes incorrectly that Vichien committed suicide and that it was partly her fault. At the end of the movie, Ton tells Pranee the truth, that Vichien's death was an accident and that Pranee should not blame herself. Ton and the boys that bullied him and told him the ghost stories are now friends and the troubles between Ton and his dad are resolved. 
