The bass for this song is pretty simple and its the pretty much the same thing
the entire sing.  Throughout the song I mix it up by dropping out the first open a on occasion
the a and a# as well.  Nothing major, just something to stop the repetitiveness of the 
 Listen to the song for the rhythm.

g|-----------------4----------------------4----------|
d|---------------4----------------------4------------|
a|-01-2--5--2--5-----1-2--01-2--5--2--5-----1-2------|
E|---------------------------------------------------|