Carlos Mencia called out a couple for being rude at his standup set ...

then he dropped his pants, took a bow and showed them his bare ass ...

and TMZ has pics from the front row. 😳 Mencia's moon went down Friday night at the Comic Strip in El Paso, TX ..

. where Carlos was performing. Folks who were there tell us a couple in the front row was completely obnoxious during Carlos' entire set -- something that clearly annoyed the comedian.

At the end of his gig, we're told Carlos put the offenders on blast, telling them he had something special for them ...

his naked butt cheeks!!! However, Carlos tells TMZ, "It was all in good fun. We took pictures and laughed about it after the show." In fact this wasn't his first rodeo, Carlos mooned a crowd on a cruise in August 2021 -- but only after Kid Rock did it first.

Forget "Mind of Mencia" ...

he's giving Moon of Mencia!!!.