Heat oil in a soup pot over medium-high heat. Add bacon, if using, and lightly brown. Add onions, garlic, celery, bell pepper and corn. Season with thyme, bay and Old Bay, and cook to soften, 10-12 minutes, stirring occasionally. Add chipotle, tomatoes and stock and simmer together a few minutes. Season with salt and pepper to taste.
To serve, divide tortilla chips among four soup bowls. Top with cheese, avocado and a squeeze of lime then ladle in soup and garnish with cilantro or parsley.