Combine salt, cayenne pepper, white pepper, black pepper, and dried thyme leaves in a small container.

Heat vegetable oil in a cast-iron skillet until very hot.

Whisk in flour and stir constantly until a dark brown and smooth roux forms, being careful not to scorch.

Reduce heat and stir in chopped celery, onion, bell pepper, and seasoning mix.

Puree vegetable soup in a blender.

Add water to the pureed soup until it equals 2 cups.

Add the soup mixture and crawfish tails to the skillet.

Simmer for 10 minutes.

Serve hot over rice.