Thre are two chord progressions in the song
1st one: Am, C, D, F, A, C, E
2nd one: Am, C, D, F, A, Em, A
Just go on playing it one after another throughout the song!!!
Now to the bass line:
Pick each note once, see the guitar tab for reference:
Riff1 (for the first progression):
Am C D F Am C E
G|-------------------------------------|
D|-------------------------------------|
A|---0----3----5---------0----3--------|
E|------------------1--------------0---|
Riff2 ( for the second one):
Am C D F Am Em Am
G|-------------------------------------|
D|-------------------------------------|
A|---0----3----5---------0---------0---|
E|------------------1---------0--------|
It is just the basis, though the band played it that way.
PLAY TOO ..