Pla Ra is the Isaan Thai name for this product and Padaek is the Lao name also used by Isaan people.

As described by Wan Srikhamthae (Ubon Ratchathani/Bangkok)

There have been many enquiries coming through search engines to EdiblyAsian looking specifically for a recipe for Thai or Lao fermented fish ingredient. If you are unfamiliar with this ingredient it's description may not sound appetising but it is an essential ingredient in certain (not all) Lao and Isaan recipes. Fish are allowed to ferment over an extended period in earthenware masons. After the fermentation the fish has been transformed into a very soupy brown mixture. Aspects of the carcass can still be seen but the aroma has most definitely changed. If you were unaware of its deliberate production and came across this ingredient you would probably dispose of it immediately and possibly even burn it in a fire to kill any of the presumed nasty pathogens :) To give it legitimacy all we need to do is to classify it as a gourmet item which it truly is!  :)

For those with a taste for aged fish products it is not such a big acceptance. Fermented fish ingredients are abundant in Europe and some date back through a few millenia. This is a regional phenomena. It is seen with various modifications in Cambodia, Laos, Thailand and Burma. I don't know if Vietnam has a fresh water fish equivalent but this would not be surprising. I mentioned fresh water fish as this is the origin of the fish and not sea-fish. Ocean fish can be used for making such a product but the Lao and Isaan people have traditionally lived in areas without access to a coastline.

Basically the fish is killed cleaned and heavily salted with another product and allowed to stand lightly covered for 3 months to 1 year for the part-autolysis and fermentation to occur. The quality of the Pla Ra/Padaek is a combination on the quality and size of the fish plus the period of fermentation. It isn't seen in retail outlets beyond the region however the Cambodian product "Prahok" is commercially available in many countries. Prahok is of the same style but is rather distinct as the Cambodians have regarded Prahok as a life saving food during times of drought famine and war. They are very selective of the fish that they use in the process and have different names for the various fermented fish origin or species. Prahok can be used as a substitute for dishes that call for Pla Ra or other fermented fresh water fish. Prahok is in that stage of introduction onto the world ingredient stage just waiting for clever marketing and advertising I daresay.

The recipe is semi quantitiative because this really depends on the quantity of available fish or the quantity of fermented product a producer is looking to have available at the end of the fermentation. This recipe is still widely used in Isaan with as many variations almost as there are cooks or producers.

  • Fresh water fish. (Typically this is the Snakehead Murrell {Channa striata})
  • Salt
  • Rice husks.
  1. Gut and clean the very fresh fish, washing the body cavities, gills,  mouth and outside of the carcass with plenty of fresh running water.
  2. Descale the fish and rinse again. (It's important to have a very clean meat as a starting product)
  3. Cut the fish into large pieces filleting as you go. The head is removed.
  4. Layer  a weighed amount of fish in a large earthenware jar.
  5. Sprinkle an amount of rice husks (not cooked or treated in any way, over the fish. The amount is not truly specified but rather described as a couple of handfulls.
  6. Sprinkle the same weight of salt as the fish, directly onto this layer of fish.
  7. Repeat the layering process as for the first layer until all the fish is safely placed into the fermentation jar.
  8. Cover the mouth of the jar with porous cloth to exclude insects and vermin and cats.
  9. Leave this to ferment in an airy position but not in hot sun for a minimum of six (6) months. The longer the digestion is allowed to proceed, the higher the quality of the product.
  10. When fermentation is complete then transfer the Pla Ra (that is the entire mixture of contents into smaller glass storage jars with a lid.

I know this recipe is incomplete with respect to specific information but I couldn't glean this from the experienced cook who described this to me.
I am guessing that the high salt content prevents the chances of a pathogenic or spoiler organism competing for the fish substrate. There are many so called "halophilic" organisms that are used similarly. I suspect the helpful organism is introduced with the rice bran, similarly to that used in producing fermented soybean products. I would be most glad for any information regarding this.

I would strongly recommend that you produce this with the supervision of a person familiar with fish fermentation.