Effin foreigners. Ones foreign to Thailand I mean. Avoid them like the plague. Most people seem to pack everything for their trip to Thailand except their common sense and their manners.
Bars full of Aussies, Poms and Yanks, in that order. Hate listening to their bs and about their latest exploits.
Chinese tourists. My wife and I drove into CM city the other day and I lost count how many Chinese people walked across the street right in front of us like they owned the road. The hired scooter riders who stop in the middle of Thaphea Road to look at the map are just as annoying.
Any sweaty twit of any nationality wearing a Chang wifebeater and smelling like a sumo wrestler's jock strap. They should be shot on sight, or smell.