Preheat the oven to 350°F.
In a large skillet, heat the olive oil over medium heat. Add the diced chicken and season with salt, pepper, garlic powder, onion powder, and thyme. Cook until the chicken is no longer pink, about 5-7 minutes.
In a large mixing bowl, combine the cooked rice, cream of chicken soup, chicken broth, mixed vegetables, and the cooked chicken. Stir until well combined.
Transfer the mixture to a greased 9x13-inch baking dish. Spread it out evenly and top with shredded cheddar cheese.
Cover the baking dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Let the casserole cool for 5 minutes before serving.