Kong ring
The kong ring or gung treng (Khmer: គង់រេង) is a Cambodian tube zither, in which a tube of bamboo is used as a resonator for stings that run along the outside of the tube, lengthwise. It has the same musical purpose as the "bossed gongs" (circular gongs that have a rounded bump in the center, like a shield boss) and may substitute for them and accompany singing.