Morgan Wallen allegedly tossing a chair off a rooftop is the last thing anyone would expect ... based on new images of him casually chatting up a woman Sunday night, just moments before he wound up in handcuffs.

Photos obtained by TMZ show the country star minutes before the chair-chucking incident ... and as you can see, he was talking to the woman in a black miniskirt. We're told the man in the red and black flannel is a member of Wallen's crew, who was telling patrons not to take photos.

Eyewitnesses tell us Wallen appeared intoxicated, and at least to their eyes, seemed to be flirting with the woman ... roughly 20 mins before cops cuffed him.

We're told It's unclear what exactly happened to cause him to pick up the chair and hurl it from the rooftop, as captured by multiple surveillance cameras.

But, this pic shows roughly where Wallen was standing when cops say he grabbed the chair. We've confirmed, through metadata, the shot was taken at 10:50 PM ... and police say the chair crashed onto the sidewalk below at 10:53 PM.

As we reported, the furniture landed within a few feet of officers who were standing outside the bar entrance. Safe to say, Wallen is extremely lucky no one was hurt.

Even in the midst of getting booked into jail, Morgan flashed a smile for his mug shot before bailing out early Monday morning.