In 3- or 4-quart saucepan over medium heat, sauté carrots and chopped onion in oil 5 to 10 minutes or until onion is golden. Stir in broth, cabbage, potatoes and thyme. Bring to a boil. Cover. Reduce heat and simmer 30 minutes or until vegetables are tender. Stir in SPAM®. Simmer 2 minutes.
Meanwhile, heat broiler. In small bowl, combine Swiss cheese, mayonnaise, Parmesan cheese and green onion. Spread over each bread slice. Ladle soup into oven-proof bowls.* Top each with a bread slice. Place bowls on baking sheet. Broil 3 minutes or until cheese mixture just begins to brown.
*If bowls are not oven-proof, place bread slices on baking sheet and broil, then place on top of soup.