Prior to joining the UBD in 2012, he worked full time at the National University of Singapore (NUS) from 1985. He was the previous Head of the Department of Community, Occupational and Family Medicine and Director of the Centre for Environmental and Occupational Health Research. His appointments prior to joining the NUS were Assistant Director in the Division of Occupational Safety and Health, National Productivity Board, and Medical Director in a multinational insurance company.
Dr Koh has been appointed as Visiting Professor, Adviser and/or Examiner to universities in the USA, Japan, Taiwan, Hong Kong, Thailand, and Malaysia. He has been engaged by the World Health Organization as a consultant in occupational and environmental health to countries such as Vietnam, Indonesia, and the Solomon Islands, and undertaken international consulting work with large organizations and multinational companies in the Asia-Pacific Region.
His research and teaching interests are in occupational and environmental health. He has over 250 peer-reviewed publications and had edited several books, including the Textbook of Occupational Medicine Practice, which is now in its third edition. He also serves on the advisory and editorial boards of major international occupational and environmental health journals.
Dr Koh has received international recognition for his academic work, including the Smiley medal from the Faculty of Occupational Medicine, Ireland, the Wilf Howe Prize from the Faculty of Medicine, UK, and the William J Gies award from the Journal of Dental Research, USA.