Choy was a professor in the department of chemistry at Seoul National University (1981–2004). He is currently a distinguished professor and director of the Center for Intelligent Nano-Bio Materials (CINBM) at Ewha Womans University. He held multiple visiting professorships:
* Laboratoire de Chimie du Solide du CNRS, Universite de Bordeaux I, France (1985-1986), 
* Department of materials engineering, University of Illinois at Urbana Champaign, United States (2003), 
* Kumamoto University, Japan (2008)
* Honorary professor of Australian Institute for Bioengineering and Nanotechnology at The University of Queensland, Australia.
He was a member of the international editorial board (IEB) or an associate editor of the Journal of Material Chemistry, Materials Research Bulletin, and Chemistry of Materials, and is currently involved in various journals including Journal of Solid State Chemistry, Solid State Sciences, Chemistry – An Asian Journal as an IEB member.