Spray a large skillet with Pam. In the skillet cook ham, celery, and onion till vegetables are tender. Stir in potatoes; fresh green beans if using them; water; thyme; and pepper. Bring to boiling; reduce heat. Cover and simmer for 20 minutes or till potatoes are tender and most of the liquid is absorbed. If using frozen green beans, add to ham and potato mixture the last 7 minutes of cooking. To serve, sprinkle with Parmesan cheese.