Heat oven to 350°F. In medium bowl, mix chicken, sugar, salsa, enchilada sauce and corn.
Place tortilla chips in ungreased 8-inch square (2-quart) glass baking dish. Top with chicken mixture. Sprinkle with onions, tomato and cheese.
Bake 35 to 45 minutes or until hot and bubbly. If desired, arrange additional tortilla chips around edge of dish.