I just listened to this song tonight, so I don't know the entire song, but I can give you a little help right now...
It's in the Key of C...and quite a bit of it, is playing off 2 chords, the ii and vi...
m9th chords
D-A-D/F-A-C-E
A-E-G/B-C-E-G
The bass run I was hearing with chords could be any of the following (if you have to play bass line)...depends on alteration of chords
(D, A, C, Db, D,) or (D, A, D, Eb, E) or (D, A, D, E, F)
(A, E, G, Gb, A,) or (A, E, A, Bb, B) or (A, E, A, B, C)
This was just a quick observation, I haven't listened to the entire song in depth, but hopefully this will help to be a starting point.