Dr Sim obtained his basic medical degree (MBBS) from the National University Of Singapore in 1996. He received his Emergency Medicine training at the National University hospital. He obtained his postgraduate degrees in Emergency Medicine (Membership of the Royal College of Surgeons) in 2002. He completed a half year attachment programme with Cleveland Clinic Foundation Observation Medicine starting December 2006 under the mentorship of Dr Sharon Mace. 

Dr Sim currently practices as a Senior Consultant at the Emergency Medicine Department, National University Hospital. He is the deputy director of the observation medicine unit. He also serves at the Urgent Care Centre at Alexandra Hospital. 

Dr Sim has special interest in acute medical care particularly endocrine and cardiac emergencies. He is trained in 2D Echo and proficient in Focused Assessment with Sonography Trauma (FAST).

He is a clinical tutor with the Yong Loo Lin School of Medicine, National University of Singapore, and an Advanced Cardiac Life Support (ACLS) Instructor. He has also given lecture for the Master of Emergency Medicine Preparation course.