Pierce potatoes with a fork several times; bake in a preheated 400°F oven 1 hour or until fork tender; cool slightly. Peel, if desired; cut into 1-inch cubes.
Meanwhile, in large saucepan or Dutch oven over medium heat, sauté bacon until crisp; remove to paper towels. Drain off all but 1 tablespoon bacon drippings.
Add onions to pan; sauté until onions are softened (about 3-5 minutes). Add chicken broth, mashed potato flakes and thyme; salt and pepper to taste. Bring to a boil; reduce heat and simmer 5 minutes.
Stir in diced potatoes, half & half and cheese; simmer 10 minutes. Remove from heat; stir in bacon and green onions.