Most of my favourite Thai curries are coconut based. But there are a couple of spicy ones that are not. The most famous is probably gaeng som, which is a sour soup. It is a bit like a thick vegetable soup that we have back home but it is both hot and sour. For a long time I always thought that this soup was called gaeng som because it looked orange. So, I always referred to it as the orange soup. But reall, here "som" means "sour" even though it is spelled the same.
You will find lots of different recipes, though it is often seen with either fish or, in the above case, with prawns. The vegetables in this version are long beans, Chinese cabbage and carrots. The paste is made up with red chilis, chopped red shallots and shrimp paste. The ingredient that is mainly responsible for making it sour is the tamarind juice. A good side dish for this spicy soup is omelette. Try it, it is a different experience