Kaeng som is probably the most well known southern dish within Thailand. Kaeng som is actually the name of a similar central Thai dish, so central Thais tend to refer to the southern version as kaeng lueang, or “yellow curry”, because of its color. This is not to be confused with the yellow curry that most foreigners are familiar with, which is a coconut-milk based curry of Indian origin called kaeng karii “curry curry” by Thais. Confused? Good, now we can begin.
Kaeng som (which I will continue to call it here) actually translates as “sour curry”, but the predominate taste is usually that of spicy. Very spicy. I consider this to be probably the spiciest curry in the country (which says a lot in a country of spicy curries!). The curry paste consists of a few simple ingredients, and the soup consists of fish (or other seafood) and typically one kind of vegetable (or fruit). That’s it.
Put the curry paste aside and prepare the soup ingredients. Thinly slice sour, slightly unripe pineapple, about 1 cup. Clean and cut some fish into bite-size pieces until you have about 1-1 1/2 cups. I’m using a kind of fish known as plaa kraphong (sorry, can’t recall English name), which is the most common fish used in this dish. I reckon any white-fleshed sea fish will do. Set both of these aside. For your mise en place you’ll need a bottle of fish sauce, 3-4 sliced limes ready for squeezing, and some sugar.
Bring about 3-4 cups of water to the boil, add about half of the curry paste and stir and simmer until the broth is fragrant. Add more curry paste if necessary, but don't add it all at once as it may be too much!
Squeeze a few limes’ worth of lime juice into the broth until you reach a tolerable state of sourness.
Remember, it is called “sour” curry, so there should be a definite sour taste, followed by spicy, salty and sweet. Add some fish sauce if it isn’t salty enough.
I like using pineapple in this dish as it adds a wonderful sweet flavor, but a variety of other veggies can be used, including pickled bamboo (very common and extremely sour) or slices of unripe papaya.