[2] Playing for several clubs in the National Premier Leagues Western Australia youth divisions, Riak moved to Melbourne and signed with Bentleigh Greens, where he assisted the club to a Round of 16 spot in the 2022 Australia Cup, where despite Riak scoring a 86th minute consolation goal,[3] they were knocked out 2–1 by A-League Men heavyweights Sydney FC.
[4] Riak's strong performances for Bentleigh in both the Australia Cup, and the NPL Victoria saw former National Soccer League champions South Melbourne secure his signing for the 2023 season.
[5] After further strong performances for South Melbourne throughout the 2023 NPL season, Riak secured his first move overseas, and ultimately professional contract when he signed for PSS Sleman in 2023–24 Liga 1.
[7] His signing came alongside fellow African Australian Elvis Kamsoba who had recently been released from Iranian club Sepahan.
[9] Riak accepted a call up from South Sudan under manager Stefano Cusin, making his full international debut against Congo in the 2023 Africa Cup of Nations qualification.