Melt butter in heavy large skillet over medium-low heat. Add onion and bell pepper and saute until tender, about 8 minutes. Add corn and tomato and saute 3 minutes. Add rice, 1 cup cheese, cream and thyme and stir until cheese melts and mixture is heated through. Transfer mixture to 8-cup souffle dish.

Preheat broiler. Sprinkle remaining 1 cup cheese over rice mixture. Broil until cheese melts, about 2 minutes.