Cook bacon in a large Dutch oven until crisp. Remove with a slotted spoon and set aside, leaving bacon grease in the Dutch oven.
Add shrimp and 1 teaspoon Cajun seasoning and cook until shrimp just turn pink, about 2 to 3 minutes. (they can be a little undercooked at this point. The heat from the chowder will continue to cook them when you add them back in.) Remove shrimp with a slotted spoon and set aside with bacon.
Add onion, red bell pepper, and celery to Dutch oven and cook 5 minutes, stirrinng occasionally.
Add garlic and cook 1 more minute.
Sprinkle flour over veggies and cook and stir for 1 minute.
Gradually whisk in broth.
Add remaining Cajun seasoning, thyme, black pepper, cubed potatoes, and corn. Bring to a boil and then reduce heat to a simmer. Simmer for 15 minutes or until potatoes are soft.
Stir in heavy cream and simmer for 2 to 3 minutes.
Stir in shrimp and bacon. Serve in bowls and garnish with green onion.