Khing ohn is a Thai term meaning "young ginger".
It refers to a ginger root which has not yet matured. It has a yellow skin that is not wrikled or hard. It taste milder and less hotter like the old ginger.
Young ginger is light in color and often comes with some green stem attached. It is often pickled and eaten with other food. You've probably seen it served with sushi - it is the pink one. It can also be pickled with other vegetables like eggplants and cucumber and served with rice.