Lightly coat a 3-1/2- or 4-quart slow cooker with cooking spray; set aside.
In a large bowl beat cream cheese with an electric mixer on medium to high speed for 30 seconds. Add eggs; beat until nearly smooth. Stir in frozen corn, cream-style corn, onion, and thyme. Add muffin mix, evaporated milk, and butter; stir just until combined. Spoon mixture into prepared cooker.
Cover and cook on high-heat setting for 2-1/2 to 3 hours. Remove crockery liner from cooker, if possible, or turn off cooker. Cool pudding, uncovered, for 15 minutes before serving. Sprinkle with tomatoes.