Arrange the chicken thighs in a large 9x13-inch baking dish or a roaster.
Pour the chicken broth over the thighs. Sprinkle the onion soup mix and brown sugar evenly over each thigh then squeeze ketchup over each thigh. If you don't have a squeeze ketchup bottle, spoon about 1/2 tbsp of ketchup over each thigh.
Cover the pan with aluminum foil and bake for 45 minutes. Remove the foil and bake for another 10 to 15 minutes or until the skin is crispy and chicken is cooked through. Bone-in thighs should reach an internal temperature of 180 F degrees when they are done.