Place the lima beans into a large container and cover with several inches of warm water; let stand 1 hour. Drain.
Fill a large pot with lightly salted water and bring to a rolling boil over high heat. Add the ham hocks and return to a boil; cook at a boil for 1 minute. Drain and rinse.
Combine the lima beans and ham hocks in a stockpot; add the ginger, tomato, onion, green chile peppers, tamarind powder, and 3 cups water. Season with salt to taste. Bring the mixture to a boil; reduce heat to medium-low and simmer the soup until the pork is tender and the lima beans are soft and bursting from their skins, about 20 minutes. Add the spinach to the soup and cook until the spinach has just wilted.