Heat olive oil in a large pot over medium heat. Add onion, bell pepper, and celery, and sauté until softened.

Stir in garlic and cook for an additional minute.

Add chicken broth, diced tomatoes, Cajun seasoning, thyme, and bay leaves. Bring to a boil.

Reduce heat and let simmer for 30 minutes.

Add shrimp and crab legs, cooking until shrimp are pink and cooked through.

Remove bay leaves and serve hot, garnished with green onions.