I just buy the packets in the asian section all you do is boil water and add the packet. I also get the egg flower where you add an egg to the mixture while it is boiling. It is super easy if you don't want to take too much time. It is not as good as homemade but only takes 5 min and is pretty good.
Ok, I haven't tried this, but it's from a Thai cookbook I have:
Hot-and-Sour Prawn Soup (Tom Yam Kung)
Serves 4-6
1 lb raw jumbo shrimp, thawed if frozen
4 c chicken stock or water
3 lemon grass stalks, roots trimmed
10 kaffir lime leaves, torn in half
8 oz can straw mushrooms, drained
3 TB Thai fish sauce
4 TB fresh lime juice
2 TB chopped scallion
1 TB fresh cilantro leaves
4 fresh red chillies, seeded and thinly sliced
salt and ground black pepper
1. peel the prawns, reserving the shells. devein and set aside
2. rinse the shells under cold water, then put them in a large pan with the stock or water. bring to boil.
3. bruise the lemon grass stalks and add them to the stock w/ half the lime leaves. simmer gently for 5-6 minutes, until stock is fragrant.
4. strain the stock, return it to the clean pan and reheat. add the drained mushrooms and the prawns, then cook until the prawns turn pink.
5. stir the fish sauce, lime juice, scallion, cilantro, chillies and the remaining lime leaves into the soup. taste and adjust as necessary. the soup should be sour, salty, spicy and hot.