Fried Fermented Fish (Pla Som Tod)

Ingredients

Equipment Needed

• •Large glass jar or food-safe container with tight-fitting lid (for fermentation)
• •Deep pot or wok for deep-frying
• •Spider strainer or slotted spoon
• •Wire cooling rack

Instructions

1. 1

   Prepare and salt the fish

   Rinse each fish under cold water and pat completely dry. Score both sides with deep diagonal cuts, about an inch apart, cutting almost to the bone. These scores aren't decorative. They let salt penetrate the flesh and give bacteria access during fermentation. Rub the coarse salt generously over the entire fish: inside the cavity, into every score mark, across the skin. Use all three tablespoons across the four fish. Set them on a plate and let them sit for 15 minutes while you prepare the fermentation base. The salt starts drawing moisture immediately. That's what you want.

   Score deep. Shallow cuts do nothing. You need the salt and the garlic-rice mixture to reach the flesh. If you can see the bone through the cut, you're in the right territory.
2. 2

   Pack the fermentation

   In a bowl, mix the crushed garlic cloves with the cooled cooked rice. Use your hands. Squeeze the garlic into the rice so the juices distribute through the grains. This mixture is the fuel for your fermentation: the rice provides carbohydrates for lactic acid bacteria to eat, and the garlic provides both flavor and mild antimicrobial properties that favor the right bacteria over the wrong ones. Stuff each fish cavity with the garlic-rice mixture, pressing it in firmly. Pack the remaining mixture into the score marks and over the surface of the fish. Layer the fish tightly into a glass jar or food-safe container. Press down to eliminate air pockets. Seal the container tightly. Leave at room temperature (ideally 28-32°C, which is normal Thai room temperature) for 3 to 5 days.

   The rice MUST be fully cooled before packing. Warm rice accelerates the wrong kind of bacterial activity and can spoil the fish before the lactic acid has time to drop the pH. Cool rice. Room temperature. That's the rule.

   In cooler climates (below 25°C), fermentation will take longer, possibly 5 to 7 days. The bacteria work slower in the cold. Be patient. Check by smell and texture, not by calendar alone.
3. 3

   Check fermentation and fry

   After 3 days, open the container and check. The fish should smell distinctly sour and tangy, with a funky edge that's sharp but not rotten. The flesh should feel firmer than raw but still yielding. The rice will have broken down and turned slightly translucent. If it smells cleanly sour, like yogurt crossed with something briny, you're there. If it smells putrid or like decay, something went wrong: discard it. Trust your nose. Once the fermentation is right, remove the fish and gently rinse off the excess rice and garlic under running water. Pat the fish bone-dry with paper towels. Dip each fish in beaten egg, coating all surfaces. Heat vegetable oil in a deep pot or wok to 170°C (340°F). The oil should be deep enough to submerge the fish. Fry 2 fish at a time, turning once, until the skin is deeply golden and crispy, about 4 to 5 minutes per batch. The egg coating will puff and turn golden. When you tap the skin with a spatula, it should sound hollow. Drain on a wire rack, not paper towels. Paper towels trap moisture underneath and kill the crispness you just worked for.

   Unlike naem, which is eaten raw after fermentation, pla som is ALWAYS fried before eating. The deep-frying provides an additional safety margin beyond the lactic acid preservation. This is a cooked fermented product. Don't eat it raw.

   Oil temperature matters. Too hot and the egg coating burns before the fish heats through. Too cool and the fish absorbs oil and turns greasy instead of crispy. 170°C is the target. If you don't have a thermometer, drop a small piece of egg into the oil. It should sizzle immediately and float within 2 seconds.
4. 4

   Serve with sticky rice

   Plate the fried pla som whole. Serve immediately alongside sticky rice (khao niew), raw cabbage wedges, sliced cucumber, and fresh bird's eye chilies (prik khi nu). This is Isan eating. You tear the fish apart with your hands, pinch some sticky rice, grab a piece of cabbage, bite a chili if you want heat. No utensils, no plating rules. The sour tang of the fermented fish against the neutral sweetness of sticky rice is the combination. The raw vegetables are palate cleansers between bites. Every element has a job. Eat it the way it was designed to be eaten.

Chef Tips

• •The fermentation endpoint is everything. Three days gives you a mild, pleasant sourness. Five days gives you a deeper funk that hits you in the back of the throat. Both are correct. It depends on your tolerance and your taste. Start at three days for your first batch. Next time, push it further. You'll find your preference.
• •Silver barb (pla tapian, ปลาตะเพียน) is the traditional fish for pla som because its firm flesh holds up during fermentation without turning mushy. Tilapia is the easiest substitute outside Thailand, same firmness, similar size, widely available. Avoid soft-fleshed fish like catfish. They fall apart.
• •The egg coating before frying is standard in most Isan households. It creates a crispy golden shell that protects the sour flesh inside and adds richness. But some vendors skip it entirely and fry the fish bare. Both methods are traditional. Without egg, the skin gets more directly crispy but the fish dries out faster. With egg, you get that puffed, golden armor. I use egg. My mother used egg. You should use egg.
• •Pla som keeps in the refrigerator for up to a week after reaching your desired fermentation level. The cold slows the bacteria dramatically but doesn't stop them entirely. Fry within a week. After that, the texture degrades and the sourness becomes overpowering.
• •This is one of three major Isan fermented products alongside naem and sai krok Isan. Each has a different endpoint. Naem is eaten raw. Sai krok Isan is grilled. Pla som is deep-fried. The fermentation science is the same. The finishing technique defines each product. Understanding that distinction is understanding the system.

Advance Preparation

• •The fermentation requires 3 to 5 days at room temperature before the fish is ready to fry. Plan accordingly. This is not a same-day dish.
• •Once fermented to your desired sourness, the fish can be refrigerated in its container for up to a week before frying. The cold slows fermentation but doesn't stop it, so the sourness will continue to develop slightly.
• •Fry immediately before serving. Fried pla som loses its crispness within 20 minutes. There is no reheating method that restores the texture. Fry it, eat it.

Frequently Asked Questions

Nutrition Information

1 serving (about 210g)