Well, there was a book called "Off the Rails in Cambodia".
I guess if you avoid that crowd, you won't witness it first hand.
I just watched a video of a Youtuber living in Cambodia mention this.
And I just did a google search and found this article:
https://english.cambodiadaily.com/news/when-the-needle-and-the-damage-are-done-a-difficult-diagnosis-awaits-771/
It was in this wobbly wooden house built over the water that 26-year-old Kieran Power died on April 29. Friends living nearby said he overdosed on drugs, the culmination of a weeks-long spiral into depression and substance abuse brought on by losing his job as an English teacher.
Power was one of an increasing number of foreigners drawn to Boeng Kak by the area’s reputation for cheap accommodations, weak law enforcement and easily available drugs. He was also on a growing list of Westerners who have died in grim circumstances among the maze of unsurfaced alleys and budget guest houses that lines the eastern shore of Phnom Penh’s largest lake.