Forget the heavy bag ... PowerSlap star turned boxer Abby Montes is gettin' ready for her pro debut in a much hotter way, slappin' OnlyFans models' asses!

Montes was at a mixer for fighters, ring girls, and creators involved in Wednesday’s Knockout Queens influencer boxing event when some of the girls found out about her real day job -- an undefeated slap fighter.

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The second they heard, a couple of the OnlyFans models lined up like it was a meet-and-greet photo op, and Abby didn’t hesitate, delivering her signature heavy-handed slaps straight to the booty.

Among the OF models ... Alanna Jade, who will be a ring girl for the event, and Cookie, who isn't working the card, but why the hell not still get slapped?!

We even secured some video ... and it looks like everybody had a GREAT time!

As for the KQ event -- going down from the Coachella Valley -- it won't only feature influencers and content creators ... Montes is making her professional boxing debut.

Knockout Queens streams on Wednesday on Triller, Kick and TikTok.