In a slow cooker, combine water, chicken broth, soup, uncooked wild rice, thyme and pepper. Stir with a large slotted spoon or whisk. Cover and cook on high for 4 hours or low for 8.
Prior to the 4 or 8 hours, cook and cube chicken into bite size pieces. When you have 30 minutes remaining, carefully transfer chicken to slow cooker using a slotted spoon. Stir soup well. Cover and cook for the remaining 30 minutes.
Meanwhile, shred 2 cups of baby spinach. Just before serving, sprinkle spinach over soup and stir to combine. Serve warm.