He's playing some two or three-note harmonies (diads or triads) moving down the neck, highlighting the chord changes / scale. It's kind of muddied up in the recording / performance, but that's basically what it is.

E---10---9----7---5

B---10---10---8---5

G---11---9----7---6

D---12---11---9---7

A--x

E--x

In this case it would be various positions / inversions of D major, A Major, G Major, and back to A Major to create a melodic line.

Something like that, anyway. It looks like he's making some mistakes in the video so hard to tell exactly.

-Carl.