Place the stock or water in a pot and heat. Add the galangal, lemongrass, lime leaf, nam prik pow and chillies. Simmer the pot until the soup is fragrant, about 15 minutes.
Add the Carnation and cherry tomatoes and cook until the tomatoes are soft. Add the prawns. While the prawns are cooking, smash their heads with the back of a spoon and squeeze out the goodness inside. Add the squid and herbs.
As soon as the squid is cooked, season the soup with the fish sauce and lime juice. Serve immediately.