Preheat your oven to 375°F.
In a large mixing bowl, combine the shredded chicken, frozen mixed vegetables, cream of chicken soup, milk, garlic powder, onion powder, thyme, salt, and pepper. Mix until well combined.
Spread the chicken mixture evenly in the bottom of a greased 9x13-inch baking dish.
Sprinkle the shredded cheddar cheese evenly over the chicken mixture.
Unroll the crescent roll dough and lay it over the top of the casserole, pinching the seams together to create a crust.
Bake in the preheated oven for 25-30 minutes, or until the crescent roll dough is golden brown and cooked through.
Let the casserole cool for about 5 minutes before serving.