four friends go on rafting, adventure goes wrong, one sinks and dies, rest somehow escape, dead friend returns to their tent at night, they run away in horror to find their own dead bodies lying near the river.
The third segment titled “The Man in the Middle” of the 2008 thai horror anthology film “4bia” (also known as “Phobia” or “See prang”):
https://www.imdb.com/title/tt1292575/
Detailed plot summary on Wikipedia here:
https://en.wikipedia.org/wiki/4bia
Quotes from the above Wikipedia page:
“Four rafting-lovers, Aey, Ter, Shin, and Phuak are rafting in a lonely jungle in Chiang Mai.”
“The next day, when they are swimming in the river, Aey drowns and cannot be located.”
“Shin then finds Aey’s body. Frightened, they go running in the woods but are shocked to find their own dead bodies. It is revealed that all of them had died when the raft crumpled over, but only Aey accepted his death, while the rest continued to ignore the fact that they had died.”
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