He made his re-debut for the Stags in a 2017 AFC Champions League qualifying play-off against Filippino side Global FC and had a chance to net on his debut but his penalty was pushed away by the goalkeeper as the Stags crash out following a 2–0 defeat. His first appearance in the league, which was also a Singapore Community Shield match, ended in a similarly disappointing fashion as he came off the bench in a 2–1 defeat by Albirex Niigata Singapore FC. Khairul came off the bench and scored the winner and his first goal of the season during the Stags' first game of the 2017 AFC Cup campaign. He scored his first goal in the league in a 2–1 win over Hougang United FC.