in a large saucepan,saute the onion,celery and red pepper in butter until vegetables are crisp-tender.stir in flour and dressing mix until smooth;gradually stir in milk.bring to a boil;cookand stir for 2 minutes or until thickened.add the potatoes,corn,ham,and thyme.bring to boil.reduce heat;simmer,uncovered,for 8-10 minutes or until heated through.sprinkle with cheese before serving.