Heat oil in a large saucepan over medium heat. Mix in shallots, garlic, crushed red pepper, and turmeric. Cook and stir until shallots are tender, about 5 minutes. Pour water into skillet, and mix in lemon grass and tamarind juice. Season with salt. Bring the mixture to a boil.
Stir snapper into boiling mixture. Cook 10 minutes, or until fish pieces are easily flaked with a fork.