Heat olive oil in a dutch oven or soup pot over medium heat. When shimmering, add the leeks, celery, carrots, garlic, salt, pepper, and thyme. Cook, stirring, until the vegetables are tender, 5 to 7 minutes.
Add the ghee and melt then, add the tomato paste. Cook, stirring, until well combined, about 2 minutes.
Stir in the seafood stock and increase heat to bring the pot to a boil. Add the diced potatoes and bayleaf and reduce the heat to a simmer. Cook, covered and simmering, until the potatoes are fork tender, 12 to 15 minutes.
Discard the bayleaf. Using an immersion blender, blend until the soup is smooth. Or, alternatively, transfer soup in batches to a food processor or blender and blend until smooth.
Bring the soup back to a simmer and stir in the coconut milk, fish sauce, lemon and hot sauce. Add the shrimp pieces and stir to combine. Cook, stirring, until the shrimp is just cooked through, about 3 minutes.
Taste and add more salt and/or hot sauce to your soup, if desired.
