Cambodia, កម្ពុជា (Kampuchea) is possibly the only country where you can spend fish. The local currency, រៀល (riĕl) , introduced in 1953 when the country gained independence from France, is believed by many to take it's name from a variety of fish, Henicorhynchus entmema or 'riĕl'.
Rial harvest
Others dispute this, claiming implausibly that the name is derived from the Spanish real, although they struggle to explain how or why a bunch of southeast Asian peasants, newly liberated from French colonial rule, suddenly took up speaking Spanish.
Whatever, the story does indicate the importance of the fish in Cambodia. It is this species, caught in Tonle Sap Lake, that is used in their ubiquitous fish sauce, ប្រហុក (prahok).
Mud carp, រៀល (riĕl), are fermented with salt as usual and both the resulting juices and the residual fish are sold as ប្រហុក (prahok).
Prahok (centre)
Although they can't agree on the etymology of their cash, everyone agrees the prahok stinks. Of all the fermented fish products, this is probably the most notorious.
Prahok is also used in the preparation of ទឹកត្រីb (tuk trei), Cambodia's version of the dipping sauces found all over SE Asia, mixed with lime juice, garlic and chilli. In fact, Cambodia has many versions of this, depending on the added ingredients.
Note: Khmer transliteration has never been standardised, so you will see various spellings of all these terms.
Images from Phnom Penh Post