Bring salted water to a boil in a large stock pot. Add sweet potatoes and cook for 5-10 minutes until tender. Drain and set aside.
In the same pot, heat oil over medium-low. Add onion and cook for 2-3 minutes until fragrant. Add garlic and ginger. Cook for another 1-2 minutes. Add curry paste and fish sauce and stir until well combined.
Pour the seafood stock and coconut milk into the pot. Simmer gently for 25 minutes.
While broth is cooking, steam clams for approximately 5-7 minutes. Remove from shells and chop if desired. Stir in sweet potatoes and clams. Garnish with basil and lime wedges and serve.
Notes
Prep the broth ahead of time and bring to the beach to re-heat on your camp stove or beach fire. Clams can be steamed directly in broth.