Place chicken thighs in the chicken stock in a large pot. Bring to a boil over medium heat, cover, and simmer until the chicken thighs are no longer pink at the bone, about 20 minutes. Remove chicken, and set aside to cool. Stir in the potatoes, tomatoes, beets, carrot, cabbage, onion, garlic, red wine vinegar, tomato paste, and bay leaf. Cover and simmer until the potatoes are tender, about 30 minutes. Meanwhile, chunk the chicken, and discard the bones. Return the chicken thighs to the soup, and simmer uncovered for 20 minutes. Season with salt and pepper.
