Natural ventilation has been appraised as the main strategy in environmental control of airborne infection in resource-limited healthcare facilities. While natural ventilation offers a low-cost alternative in diluting and removing contaminated air, its’ performance in actual settings is not fully understood. This paper reports a cross-sectional field study of six hospitals in Thailand with an emphasis on ventilation performance of naturally-ventilated hospital wards and AII rooms. The results showed that ventilation rates of 3-26 ACH could be achieved in hospital wards. Higher ventilation rates of 16-218 ACH were found in AII rooms. Our measurements also showed that a few locations within hospital wards had little or no air movement due to existing hospital ward designs. This study concludes that natural ventilation is suitable for resource-limited hospitals in tropical climates when windows are opened and exhaust fans are installed. Design guidelines that promote natural ventilation were discussed.