Mass vaccination is crucial for achieving herd immunity and controlling pandemics. Simulation models predict vaccination outcomes. This study evaluates efficiency and designs a tailored vaccination plan for Thailand. Data was derived from a COVID-19 Mass Vaccination Hub (MVH) in Chiang Mai, Thailand. It was taken between June 2021 and December 2021. The discreet event simulation model is developed in Arena Simulation Enterprise Suite version 14.0. The operational efficiency of Chiang Mai University Mass Vaccination Hub (CMU-MVH) was 1,073 vaccinations per 8 hours with 38 service staff. The average processing times (APT) were 2.5 minutes for the registration station, 12.2 minutes for the assessment station, 8.3 minutes for vaccination, and 28.2 minutes for observation. With 100% staff availability and staff utilization ranging from 0.5 to 0.7, the CMU-MVH could handle 180 to 230 vaccinees per hour or 1,227 to 1,527 vaccinees per day. Reduced staff availability leads to an increase in average processing time, especially when staff availability is lower or equal to 60%. The CMU-MVH could handle approximately a thousand vaccinations within 8 working hours. This capability could assist policymakers in developing more effective strategies and planning for future mass vaccinations. The data that support the findings of this study are available from the corresponding author, upon reasonable request.