Post Malone is taking sides in the Logan Paul-KSI boxing match ... and Logan ain't going to like this ...
The "Better Now" rapper says he's got KSI in the superfight ... telling TMZ Sports if he had to be in one boxer's entourage for the August 25 tilt in England, he's siding with the smaller dude.
"KSI looks tough," Post says. "He's tough. He's undefeated!"
Post seems irked by the way Logan and his brother, Jake, came out for the mega-fight's press conference ... saying it all looked a lot like Conor McGregor.
Regardless ... Post says he's trying to attend the fight -- giving more legitimacy to those saying this could be BIGGER than McGregor vs. Mayweather.