Preheat the oven to 400 degrees F (200 degrees C). Place chicken thighs in a 9x13-inch baking dish.

Toss potatoes, Brussels sprouts, and garlic together with olive oil in a bowl until vegetables are lightly coated. Add vegetables around and between chicken thighs in the baking dish. Season with salt, pepper, and thyme. Evenly pour the entire packet of ranch seasoning over chicken and vegetables. Sprinkle chopped bacon on top.

Bake in the preheated oven until chicken is no longer pink at the bone and the juices run clear, 30 to 35 minutes. An instant-read thermometer inserted near the bone should read 165 degrees F (74 degrees C).

Set an oven rack about 6 inches from the heat source and preheat the oven’s broiler. Place the baking dish under the broiler and cook until chicken skin becomes golden brown and a bit crisp, 2 to 3 minutes.