If someone is making fun of you there are many things that you can do.
The first one is just to ignore him and say "Yeah... sure" and continue with your conversation. This is hard for some people because they are getting nervous so it doesn't come natural but if you know how to do it - it works great (because the less you care about what he says the cooler you look).
Think of Brad Pitt. If he walks into a cafe and someone makes a joke about him would he care? Probably no.
Another way is just to change the Frame. This means that if for example he tries to make you look funny in front of everybody you view his actions as an attempt to prove himself to you.
Example:
He: Nice shirt. My sister has the same.
You: Ha-ha. You're funny. I like you but you don't always have to amuse people to make them like you.
This way you subcommunicate several things: you are used to people trying to make you like them, he is trying to get your approval and you show you are friendly, social and don't care too much about his jokes.
Now if he becomes hostile - it's socially unacceptible and will look like an asshole - you can ignore him.
If he continues with the jokes - they all fall into the same frame that he's trying to impress you and befriend you - he will look stupid so you can say: "Alright joke guy. Enough already. We all here like you.".
Or if he stops joking and begins to explain that he's not trying to befriend you - tell him "Oh... stop explaining yourself to me. It's cool." and then turn around and continue your conversation.
The third way is to be really sarcastic or over-dramatise it. If someone makes fun of you - find their purpose. Usually it is either to make you feel bad or they want to look cool and funny.
If it is to make you feel bad - then make a dramatic expression(or anything like that - I think you can do the acting) and say in a sarcastic monotone voice: "Alright... you ruined my day... I'm so depressed. Hope you are happy mister funny guy with the funniest jokes on the planet." or something like that. The key here is to make his attempt look funny and childish. By verbalising his intentions in a funny way you are actually making him look ridiculous.
Or if he wants to look cooler while making fun of you just say: "Oh... now you are the cool guy because of your funny jokes. Tell another one. Maybe everyone will like you better."
If you do this with the right amount of comedy in it everybody will laugh at him.
If you use some of these(if done properly) I don't think anyone will try to joke with you soon again.
