Ekpreechakul, MD, MSc, Thosporn, Wiphasiri Saiphiroonthong, MD, MSc, and Warut Chaiwong,BSc, MPH. 2021. “Letter to Editor: Quantitative Fit Test of Double Layer Surgical Masks ”. The Bangkok Medical Journal 17 (1), 70. https://doi.org/10.31524/bkkmedj.2021.15.001.