Place your thumb underneath the E string and release it so that it snaps back against the fretboard. This creates a percussive metallic sound. This is the same popping technique which is normally used by the index finger (P).
Use the above technique to play the next two examples.
Lick 77 combines the thumb popping effect with the index finger popping the octave note.
As an exercise play the above licks using the slap technique instead of the popping effect on the low G . Notice the different sound.