Well, I obviously can't say what happened, but I will say that the amount of times I've heard stories about foreigners being attacked, raped, or murdered in Thailand and how open xenophobia is pretty rampant in the country, and is fostered pretty heavily by authority and media, is huge.
Generally I would discount stories like that as ignorance or racism, someone attributing some random violence to xenophobia, but I've seen a pretty disproportionate amount of stories like this out of Thailand, as well as stories from every expatriate who lived there that I've ever spoken to.
Reading his story, it really seems perfectly in line with pretty much everything I've heard about the place. If you're a "farang" (white person) no one really cares what happens to you.
Here's one example: News Story
Prior to clubbing his pregnant wife to death, he shot this Canadian man in the head and chest, shot his pregnant wife, was released on $3000 bail, never prosecuted, and allowed to return back to work, despite the fact that forensic evidence shows that he show the man while standing over him, and that pretty much everyone who was there says the guy was pissed drunk. This is really not anything close to an isolated incident from everything I've read. I actually believe Junie entirely here.