http://www.stickmanbangkok.com/Weekly/weekly222.htm
I think it is very likely that Bangkok is more violent than it was ten years ago, but that is true of everywhere I know of.
Statistically, Thailand is not in the top 40 countries in the world for violent crime. Bangkok is far safer than London, New York and just about every other major city on the planet.
I read this article with some interest, and some of the stories are alarming, but for me if you use a little bit of common sense you will be safe in Bangkok.