Heat oven to 425°F. In 2-quart saucepan, heat soup, vegetables, chicken, garlic powder and thyme to boiling. Remove from heat; stir in sour cream. Spoon into ungreased 2-quart casserole.
Knead dough until softened and no longer crumbly. Flatten into a round. Place between 2 sheets of cooking parchment or waxed paper. Roll into a round the size of casserole top. Carefully peel off top sheet of paper. Replace paper to cover loosely. Carefully turn dough over to remove second sheet of paper. Use paper to carefully turn dough over filling; remove paper. Press crust to edge of casserole. Cut slits in several places in crust.
Bake 20 to 25 minutes or until hot and bubbly and crust is golden brown. Let stand 5 minutes before serving.