Preheat oven to 350° Fahrenheit. Spray a 13x9 baking dish with non stick cooking spray and set aside.
In a large bowl, mix together the frozen hash browns, onion powder, dried thyme, salt, pepper, and 1 cup shredded cheese.
Add the butter and cream of chicken soup to a medium saucepan. Heat and stir the mixture over medium high heat until the butter is melted. Remove the saucepan from the stove, and stir in the sour cream.
Pour the soup mixture over the hash brown mixture and mix until incorporated.
Pour the mixture into the prepared pan and top with the remaining 1 cup cheese. Bake for 1 hour or until hot and bubbly. Serve immediately.