Was he playing with her? ^__^
And the poster said, "MORE TO COME!" I'm not sure, but that's what I understood.
I think this was during their rehearsal for Lollipop.
This was during the rehearsal of "Tell Me" by JinuSean.

When he noticed Bom got lost with the choreo,
he stoppped dancing and hit her in the head lol
Looks like he said "babo" which means "fool" or "stupid" 
Then the camera moved away from them..

Funny how GD had this straight expression as if he's the dance teacher and Bom just laughed without even looking at him, so she knows what he meant right?

Cr. nikaistar@gbomsince2006

Cr. janexy@baidu via justbom

When the camera moved away from them, you can see on the screen on the stage that GD is still facing Bom's direction:
Cr. baidu

Video re-uploaded by: lovebommie@Twitter