Preheat oven to 375°F and place one pie crust in the bottom of a 9x13-inch baking dish.
In a large saucepan over medium heat, whisk together cream of chicken soup, milk, chicken broth, and flour until smooth and thickened, about 5 minutes.
Stir in chicken, frozen vegetables, thyme, garlic powder, pepper, and salt until well combined.
Pour the chicken mixture over the bottom pie crust in the baking dish.
Place the second pie crust over the top, crimp the edges to seal, and cut several slits in the top to vent.
Bake for 40-45 minutes until the crust is golden brown and the filling is bubbly.
Allow to cool for 10 minutes before serving.