Leelahavanichkul's core qualifications are in medicine, with a specialty in nephrology that initially focused on sepsis-induced acute kidney injury and expanded into immune responses against organisms, mainly through animal models. Leelahavanichkul obtained his degree in nephrology in 2004 and his Ph.D. from Chulalongkorn University in 2010. He spent five years as a visiting fellow at NIH, NIDDK, Maryland, USA, and was affiliated with the Board of Clinical Pathology in 2019. He has worked in the Department of Microbiology, Faculty of Medicine since 2011.