 He was appointed acting registrar during the absence on leave of Registrar W. A. N. Davies in December 1933, through 1935, and took on the added appointment of Sheriff in succession to D. F. J. Ess in August 1935.By 1936, Koon-Teck, who was by then Senior Deputy Registrar, was again appointed Acting Registrar of the Supreme Court in the Straits Settlements Civil Service, upon the departure of W. A. N. Davies and at this time it was thought that he would be eventually appointed Registrar.He sat for and passed in Malay in August 1936, and was appointed Registrar of the Straits Settlements High Court in January 1937.