In August 2009, Oh signed a one-year contract to play for the Singapore Slingers along with 7 other local players.

[2] As a raw young talent, his role consisted mainly of shutting down opposing team's guards.

For the 2011-2012 Asean Basketball League season, Desmond, together with Wong Wei Long and Shengyu Lim, were the first trio of Singaporeans that renewed their contracts with the Slingers on 29 November 2011.

[4] He went on to average career-highs in minutes, points, rebounds, assists, three-point field goals and steals for the 2012 Asean Basketball League season.

[5] Oh was selected as a special ABL import with the Westports Malaysia Dragons against a US Professional Basketball Alumni team, bannered by former NBA Stars Scottie Pippen, Dennis Rodman, Mitch Richmond, and Dennis 'The Worm' Rodman, on 17 July 2012.