Preheat oven to 325°F. Cook chicken in pan of boiling water until cooked through; drain. Mix with soup in medium bowl. In large casserole dish, layer ingredients as follows: 1/2 each of the tortilla chips (or enough to coat bottom of dish), chicken mixture, tomatoes and VELVEETA (or enough to cover tomatoes). Repeat layers, ending with tortilla chips. Bake for 15 to 20 minutes or until VELVEETA is melted. CAUTION: Casserole will be very hot.