Kroy Biermann -- Still Working Out ... Gunning for NFL Return (VIDEO)

Kroy Biermann says he's keeping himself in shape and wants to return to the NFL this season ... despite being cut by the Buffalo Bills back last month.

Kroy -- along with his wife Kim Zolciak and daughter Brielle -- were at LAX when the 31-year-old linebacker told us he's definitely not ready to retire.

By the way, Brielle is dating Boston Red Sox pitching prospect Michael Kopech -- who threw a 105 MPH FASTBALL back in the summer. Dude's a stud.

So, we asked how he's getting along with Kroy -- sounds like things are moving in the right direction.