When I do play with my thumb, Im usually playing the octave and third (above the octave) with my other fingers.
I'm usually the octave or some other second note (hammer octave from 7th, or play 3rd, 4th, 5th). Small hands = 2 notes atta time.

I started playing bass inna funk context, so I do lotsa, lotsa octaves. And on the ONE!