I tend to use British insults that I have picked up from British TV and Brits (there are so many Brits in Asia) over the years I think mostly because I find North American insults to be slap stick and little thought is required however the British insult may fly right over the persons you are trying to offend which makes it ten times funnier sometimes they even take it as a complement. So, here are a few I use or a regular basis generally with tourists, the Thai population and smart *** students. Sorry I have to list a lot because they are just too good and perhaps you can add them to your arsenal, enjoy.
It's a thankless job, but I've got a lot of Karma to burn off.
I don't work here. I'm a consultant.
It sounds like English, but I can't understand a word you're saying.
I don't know what your problem is, but I'll bet it's hard to pronounce.
They make medication for that.
I like you. You remind me of when I was young and stupid.
Any connection between your reality and mine is purely coincidental.
We're all refreshed and challenged by your unique point of view.
The fact that no one understands you doesn't mean you're an artist.
I will always cherish the initial misconceptions I had about you.
Who me? I just wander from room to room.
I'm not being rude. You just think you're important.
You sound reasonable... Time to up the medication.
You must be an arithmetic major; you add trouble, subtract pleasure, divide attention, and multiply ignorance.
If you were twice as smart you would still be stupid.
Do you have to leave soon? I was just about to poison the tea.
We all sprang from apes but you didn't spring far enough.
I'm looking forward to the pleasure of your company since I haven't had it yet.
Do you still love nature..... to spite what it did to you
Your parents are siblings
You are as brilliant and sane as Tom Cruse
Nice tan, orange is my favorite colour
Look you ain't funny, your life is just a joke
Why don't you shut up and give the hole in your face a chance to heal
I see you've set aside this special time to humiliate yourself in public.
I see the screw-up fairy has visited us again
You are validating my inherent mistrust of strangers.