Koo Kien Keat
Mainaky became a coach after his playing career. He coached the Malaysian National Team's Doubles department and his biggest success was bringing up Koo Kien Keat and Tan Boon Heong. He guided the pair to an Asian Games Gold Medal in Doha 2006. However, there was rumours about a fall out between Koo Kien Keat and Tan Boon Heong with Rexy as the pair requested for a change of coaches. Subsequently, he left the Badminton Association of Malaysia in 2012 after seven years and joined the Philippines Badminton Association as head coach. After about a year he left the Philippines Badminton Association and returned to his homeland Indonesia. He became Indonesia's high performance director and was basically the head of the Indonesia Badminton Team. He is currently still serving as the High performance director for Indonesia. In 2017, Mainaky left his position at Badminton Association of Indonesia (PBSI) to join Thailand Badminton Association (BAT). In 2018, Mainaky led the Thai women's team reached the Uber Cup final for the first time in their history.