The reasons that your feet are cramping could be many. The shape of your feet, the shoes you are wearing, the surfaces you walk on, the distance you walk, your weight, how well your diabetes is controlled are but a few that come to mind. ALso how good or bad your circulation is would be at the forefront of concern. Many diabeteic patients have vascular problems in the lower extremities.
I recommend you see a podiatrist for further evaluation.