Tua-ngok also known as tua-nork or tuwa gnog is a Thai word for bean sprouts
Bean sprouts are the sprouts of mung beans. They are widely available. It seems that in the East Coast, they're smaller and don't keep long in the fridge, while on the West Coast, they are bigger, but keep longer.
In Thailand, the tiny root that is hanging at the end of the sprout is picked off. It is a tedious job. But every family does it. That is not for me. Too time consuming!