This soup is made with noodles; the most commonly used type are khanom chin, fermented rice vermicelli, although kuaitiao or other noodles may be used. Beef or pork is another main ingredient, as well as diced curdled (chicken) blood cake. Chopped tomatoes give the dish a certain sour flavor and crispy roasted or fried dry chilies and garlic are added for spiciness. Another important ingredient that gives the dish its characteristic flavor is tua nao, a type of fermented soya bean that is used extensively in northern Thai cuisine and for which shrimp paste is sometimes used as a substitute. Nam ngiao is often served along with pork rinds.
The name of the dish originates either from the Thai name of the Bombax ceiba (Thai: งิ้ว; ngio) of which the dried flower cores are an essential ingredient in the soup, or from ngiao, a derogatory term used in Northern Thailand for people of Shan descent.
Although originally a Shan dish, Nam ngiao is very popular among northern Thai people north of Phrae Province and is considered one of the auspicious dishes in Lanna tradition, being served at banquets and special occasions.