I've lived in Thailand for over 20 years and have NEVER been threatened by a Thai. Of course, I live in a rural area in northeastern Thailand and don't go to bars to drink or stay out late at night. I also have been married to a Thai woman for most of that time, so I also don't go looking for street sex. These are the scenarios that I assume Farangs are engaged in when they are threatened by Thais.
I have been threatened by Farangs a couple of times, but that was over disputes about golf at my golf club. These threats have never come to blows or have led to any retaliation.