In 3- or 4-quart saucepan, saute carrots and onion in oil over medium heat 5-10 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 onions. Spread over each slice of bread. Ladle soup into oven-proof bowls. (If bowls are not oven-proof, place bread slices on baking sheet and broil, then palce on top of soup.) Top each with a bread slice. Place bowls on baking sheet. Broil 3 minutes or until cheese mixture just begins to brown.