yes, you can.

Let me show you the answer. H-1B can be full time or part time. You may work part time with H-1B even you do not have any other full time H-1B engagement. I am currently on H-1B, which is only 25 hours per week and I don't have any full time H-1B. However, if you wanna change from full time to part time, you need to let CIS know by filing petition.