Donghae tries to help out Sooyoung by showing her the note.

Donghae uses one hand to support/hold on to Sooyoung's hand/wrist and he uses the other hand to point at the words she has to read.

Kris sees everything taking place and look at EXACTLY where he's looking.

He looking at the hands, not the faces or anything else.

This is that moment in the video when he hesitates before he smiles

0:30

Side note:

Sort of the same thing happens later in the video

But this time, it's Sooyoung who is handing Kris the paper.

And Changmin sees.