In a large soup pot, water sauté the onion until it is soft.
Stir in the ginger, curry paste, and garlic and cook while stirring until well combined and fragrant, about 1 minute.
Add the carrots, stock, lime juice and bring to a boil over high heat. Reduce heat to low and simmer, covered, until the carrots are very tender, about 20 minutes.
Puree the soup in batches in a blender, using the hot fill line as a guide to reduce splatter.
Transfer the pureed soup back to the pot and place over low heat. Stir in the coconut milk and salt to taste. Simmer uncovered until the soup is heated through.
Note: If the soup is not spicy enough, add more of the red curry paste.
Serve with a sprinkling of thyme leaves.