Preheat oven to 350º F. Prepare rice according to package directions. Fold in cream cheese.
Spray a 10-inch round baking dish with non-stick cooking spray. Place 6 corn tortillas, overlapping edges. Spread 1/2 of rice mixture on top of corn tortillas. Sprinkle chopped tomatoes, onions, and half of prepared guacamole. Sprinkle with 2 tablespoons cilantro and 1/2 cup diced ham, top with shredded cheese. Repeat layers beginning with corn tortillas.
Bake 20 minutes or until cheese is bubbly. Cut in wedges and serve with sour cream, if desired.