koh had his early education at the now-defunct macritchie primary school, before going on to study at maris stella high school and hwa chong junior college. he then studied medicine at the national university of singapore, graduating with an mbbs degree in 1996. he subsequently obtained an mmed (surgery) from the national university of singapore as well as fellowships from the royal college of surgeons of edinburgh and the academy of medicine in singapore. he also received health manpower development programme scholarships from singapore's ministry of health for advanced training in the surgical treatment of inflammatory bowel diseases in edinburgh and at the cleveland clinic in ohio.