Place the bacon in a large, deep skillet, and cook over medium-high heat, stirring occasionally, until evenly browned, about 10 minutes. Pour off the bacon fat, and place the drained bacon pieces in a slow cooker.
Stir the tomatoes, clams, potatoes, onion, carrots, celery, parsley, salt, pepper, thyme, and bay leaf into the slow cooker, cover, and set the cooker on Low. Cook until the vegetables are tender and the flavors are well blended, 8 to 10 hours.
