Place the rinsed lentils, diced ham, sliced carrots, chopped celery, diced onion, and cubed potatoes into the slow cooker.
Add the chicken broth, diced tomatoes with their juice, minced garlic, dried thyme, and bay leaves.
Stir everything together, then season with salt and black pepper.
Cover and cook on low for 7 to 8 hours until the lentils and vegetables are tender.
Remove the bay leaves before serving.