Don't let them know it bothers you even the slightest bit whenever they do it or every single time they laugh at you, laugh even harder back at them. They will either get bored because of no reaction from you or they will get annoyed that they are being treated the same way they are treating you.
You can stop someone from laughing at you after pulling a prank on you by letting them know that you are not comfortable with that. You can also try to pull a prank on them to make it funny as well. Try to ignore them because if they think you have focused so much on what they did, they will still want to intimidate you.
My friends laugh at me all time because i do alot of stupid stuff. but i just laugh cause i picture myself doing that. :P Just go with it,never be afraid of being you. Or just find something else that is worst. :D
Ignore them or also make a joke out of it too. Agree with them, they hate that the most. If they are laughing at you for a particular reason, then agree with them. They won't know why you are, and they'll stop.
Ignore,Avoid,Don't do funny things,laugh about the situation and confuse them by letting them know what they say can bring you down,you could say knock it off,you could stop being around that person or letting that person effect you