Kaeng Som is made from a type of red curry paste, which could be made from dried chillies as well as from fresh chillies. Kaeng Som can be made with any kind of fish but most prefer crustaceous seafood; shrimp usually the most available and affordable. Any white fish works wonderfully. Kaeng Som is considered spicy by central, northern and north-eastern Thai people and is a regional specialty of southern Thailand. 
This dish is a coconut free curry.

This license for this great image has been kindly allowed by Julian Wright of MutMee Guest house www.mutmee.com. Nong Khai. Thailand.  


Kaeng Som curry paste
5 large not-spicy red chillies (like red jalapeno) and 10 red bird eye chillies 
5 shallots, finely chopped
10 cloves of garlic, finely chopped
a level tablespoon of kapi (shrimp paste).  ( If you don't enjoy  a strong fishy aroma/taste, you can reduce or omit the kapi)
a large pinch of salt
Pound all the ingredients of the curry paste together and set aside.
The curry paste preparation can be made somewhat easier by a first blending with an electric blender then a secondary pound in a mortar. The trick here is not to put the whole lot into the mortar at the one time. Bit by bit. This two stage method makes it easier and does recover the full flavour many commentators have made on homogenised curry pastes being inferior to pounded pastes. It saves on the fatigue of the 20 to 40 minutes pounding needed by the exclusive pestle and mortar method

Kaeng Som

1 pound shrimp, uncooked and shells on
2 cups of cauliflower, cut or broken into small floret's
2 cups radish, cut into 2 cm slices
4 cups of cabbage, cut into 2 inch pieces
7 cups water
4 tbsp sour curry paste
7 tbsp tamarind paste
10 tbsp fish sauce
5 tbsp palm sugar

In a large pot, boil 7 cups water 
Add the sour curry paste into the pot, the tamarind paste, fish sauce, and palm sugar, then bring the pot back to a boil.
Add sliced radish and continue cooking for 5 minutes.
Add cauliflower and let cook until done.
Taste the broth; add more tamarind paste, fish sauce, or palm sugar as necessary. 
Add the stem part of the cabbage, let cook for 2 minutes, then add the leafy part return the shrimp and let cook until veggies just done just done, only a minute or two.
Serve immediately (with rice).
Kaeng Som works well with just about any vegetable. Add the vegetables in the order of those taking the longest to cook to the shortest.