I think my only pet 'hate' in LOS is when a thai person talks some english, and gets it wrong , like trying to say the word 'problem'. We listen, and realise what they have said even though it is wrong.
Then, if YOU say some thai, and it is close , but not correct, they just stare at you until you get it correct
Thats about as bad as it gets for me.
Oh, and tuk tuk drivers that clap their hands and shout at you...