Preheat oven to 400°F. Spray a 13-by-9-inch casserole dish with cooking spray. Place broken tortilla chips in the bottom of prepared dish. Top with chicken, green chilies, and frozen corn. Sprinkle with taco seasoning.
In a small bowl, whisk together the condensed soup and the milk to form a smooth cheese sauce. Spread the sauce evenly over the top of the casserole.
Cover with foil and bake for 20 minutes. Remove the foil; sprinkle with the diced tomatoes and the shredded cheese.
Return the dish to the oven, uncovered, for approximately 15-20 more minutes (or until the chicken is cooked through and the cheese melts). Garnish with desired toppings and serve!
