Melt butter in Dutch oven over medium heat, stir in Old Bay seasoning.
Add sliced sausage and cook 3-4 minutes until browned.
Add onion and garlic, cook 3 minutes until softened.
Add tomatoes, chicken broth, potatoes, celery salt, and thyme. Stir to combine.
Increase heat to high and bring to a boil.
Reduce heat to medium, partially cover, and simmer 15-18 minutes until potatoes are fork-tender.
Add corn and frozen green beans, stir and cook 2-3 minutes until heated through.
Remove from heat and stir in lemon juice.
Mix cornstarch and cold water in small bowl until smooth, then stir into soup.
Let sit 5 minutes to thicken slightly before serving.