A paste called nam phrik kaeng som is prepared as a base for the curry, to which water and the ingredients are added. The preparation of this paste includes shrimp paste and shallots and all the ingredients are pounded with a mortar and pestle. This paste can be made from dry red chilies and one made from fresh red chilies. Some recipes state that large chilies should be used, others prefer bird's eye chilies. Fish or shrimp may be used as the basic ingredient. Preferred fish are those that keep their consistency after boiling, such as Channa striata or other equivalent marine fish in coastal locations. One variant uses fish eggs. Kaeng som is usually served with steamed rice. Traditional vegetables used in household preparation include drumstickpods, green papaya, and Sesbania grandiflora flowers, including the red variant of the flower in kaeng som dok khae daeng. Other locally available vegetables are used in the traditional versions such as Ipomoea aquatica and Neptunia oleracea.
History
Following the popularization of the dish, currently the favored vegetables include cauliflower, white radish, cabbage, chinese cabbage, carrot, long beans and asparagus, as well as cha omomelet. The versions using shrimp instead of fish are more popular; kaeng som with shrimp and cha-om omelet is now a standard dish in Thailand. Other types may include pineapple or seafood. The common point, however, is that coconut milk is not used in this sour curry. Believed that this type of sour soup was developed from the ancient food since Ayutthaya period was called "Kaeng ngao ngod". Which is a food that is similar to kaeng som today, assumed that it was adapted from the Portuguese soup by Maria Guyomar de Pinha, a Japanese-Portuguese-Bengali woman who was the chief of king's kitchen in the royal court of King Narai period.
Variants
Southern Thailand has its own sour curry, which is locally called kaeng som, but in the rest of Thailand is called kaeng lueang or kaeng som phak tai to differentiate it from the central Thai kaeng som. It differs from the central Thai dish through its use of tamarind paste, assam fruit and lime juice to achieve the sourness, turmeric, which gives it a yellow color, garlic, shallots. The main characteristics of the southern variant is the use of turmeric and that it very spicy, sour and salty.
In Kelantan, the Malaysian state adjacent to Thailand, the Kelantanese-Thai dish kaeng som no mai dong is a version of kaeng som with pickled bamboo.
Lao cuisine has a dish called kaeng som with different ingredients; a version of it has pork and kaeng som pla is a fish soup that includes lemongrass and mushrooms.
In Chonburi Province a version of kaeng som is made using kaffir lime as the souring agent and Solanum aculeatissimum eggplants.
