Karn Janthong came into prominence as the winner of the Pioneer Singing Contest in both 1992 and 1994 and subsequently competed in Hong Kong and Malaysia. He was also the winner of Top Star Parade in 1994 and was awarded a prize in the KPN Award in the same year to represent Thailand in a singing competition in Hong Kong.

Karn is a voice trainer for numerous singers under RS Promotion including James Reungsakdi, Podduang, D2B and Ploy and have taught many contestants to victory for the KPN Junior Thailand Singing Contest.

Karn had taught at the Gen-X Academy and was the artist manager at RS Promotion. He was a voice trainer of Academy Fantasia seasons 2-5, as well as other TV programmes including Two Tango and ER.

At present, Karn directs and teaches at E.B.O.