Charles, as the verb ‘se moquer’ is reflexive, the subject noun/pronoun and the reflexive pronoun always refer to the same person/people.

“Tu te moques de moi” - You could think of it as ‘You make yourself laugh at me ’ or something similar if it helps to understand, but the easiest way in grammar is usually not to try to understand, but just accept and acquire.

 https://progress.lawlessfrench.com/revision/glossary/verb-types/reflexive-verbs 

https://www.lawlessfrench.com/grammar/reflexive-verbs/

 https://www.wordreference.com/fren/moquer