The comments were textbook racism. Bigotry is defined in the dictionary as "obstinate or unreasonable attachment to a belief, opinion, or faction, in particular prejudice against a person or people on the basis of their membership of a particular group" in this case the group being "thai people".
As for not knowing many Thais - no, your wife doesn't count to be honest. if you have to invoke "the wife" when it comes to your association with Thai people, it's already game over. Many of us here have actual Thai friends and Thai colleagues - people we know really well and hang out with.
As for Thai driving. I don't think the driving here is that bad considering there is close to zero on the road enforcement of traffic laws. So the bad apples get to be REALLY bad with no recourse. That's what's going on her. Thai people don't really have a problem driving - there's just a lot of knobs on the road driving with impunity. The UK would be the same if you took the cops/cameras off the road.