Bangkokians were born thinking of somtum as spicy papaya salad. In the northeast, however, somtum can be made from many other kinds of local fruits and vegetables, from string beans to raw banana to green mango. Fun fact: papaya isn’t a local plant. Originating in South America (where chili also came from), papaya was first introduced to Thais during the Ayutthaya era many hundred years ago via foreign merchants
While each region has its own preference as to how much spice to put into somtum, no one can beat the palate of the Isaan. Nakorn Phanom or Ubon Ratchathani tend to mix together chili and dried chili, while other provinces such as Khon Kaen and Udonthani usually use red and green bird chili.
Today, we add lime juice to flavor our somtum. But it wasn’t always like this. Before lime became popular, Isaan folks added acidity to their somtum with an endemic plant called ma euk (hairy eggplant), as well as specific types of olive and tomato.
Fish sauce and palm sugar
Fish sauce wasn’t originally used to season Isaan-style somtum, and the same goes for palm sugar. Fish sauce was, in fact, Bangkok’s alternative to pla ra (fermented fish), the sauce Isaan natives use to add saltiness to the dish. Similarly, palm sugar, was added to Central-style somtum to please the taste buds of Bangkokians.
Fermented fish sauce is mixed into most somtums, except for Bangkokoriginated som tum Thai. Possessing a pungent smell and an earthy taste, pla ra is usually made with raw fish that’s fermented with salt and khao khua (toasted rice). Pla ra can be categorized into three types: pla ra nong (known for its distinctively rancid odor and murky black color), pla ra kaeng (has a milder taste, and watery appearance), and the mix of the two.
Did you know that Thais apparently eat so much somtum that we’ve had to import fermented crab from Myanmar? Lately, some restaurants have been using steamed crab, which many somtum lovers find too creamy to eat with pla ra, claiming that it ruins the overall flavors of the dish.