Finely chop the celery, onion, and garlic. Remove the crusts from the bread.
In a 4-quart saucepan, heat the oil on medium-high. Add celery, onion, and fennel seeds. Season with salt and pepper. Cook 6 min., until onion is golden, stirring occasionally. Add garlic and cook 1 min.
Stir in the broth, tomatoes, and bread. Heat to a boil on high. Reduce heat and simmer 15 min., until vegetables are tender and bread has fallen apart, stirring occasionally. Stir in the coconut milk and remove from heat.
In a blender in batches or with an immersion blender, purée soup until smooth. Season with salt to taste.