Khongwatmai became the youngest winner of a professional tournament when he won the Singha Hua Hin Open on the All Thailand Golf Tour in July 2013 at the age of 14.[1][2]
Khongwatmai played on the Asian Tour and Asian Development Tour in 2015. On the Asian Tour, he finished 64th on the Order of Merit, missing a 2016 Asian Tour card by one spot.[3] On the Asian Development Tour, he won the PGM CCM Rahman Putra Championship in March at the age of 15, becoming the youngest winner on that tour.[3] He also won the final tournament of the year, the Boonchu Ruangkit Championship to finish fifth on the ADT Order of Merit and earn his 2016 Asian Tour card.[3] He also qualified for the 2016 Open Championship by finishing sixth at the 2015 Thailand Golf Championship.[2]