Here's the deal ... the rapper took the stage at the Hakkasan Nightclub at the MGM Grand Saturday night to perform a few songs ahead of Super Bowl LVIII in Las Vegas.

While busting out a few of his songs, fans there to watch TS got a totally different kind of show ... the kind you usually need to pay big money to see in L.V.

Check out the video ... it appears a couple was getting down and dirty in one of the hotel rooms overlooking the venue, and they weren't shy whatsoever about having an audience.

Unclear if the couple was aware they were so visible ... but it definitely seems like it'd be obvious that everyone could see them -- hotel room windows aren't usually tinted, people!

Some of the performers apparently addressed the erotic display on the mic ... with one of the performers straight up saying, "That boy's a legend."

People on social media, however, were up in arms ... calling the whole thing uncomfortable and expecting people to have a bit more common courtesy when it comes to those intimate moments.

We don't know if the couple's faced any discipline from the hotel or even the police ... but that wouldn't be entirely unexpected given how much the attendees saw.