OBJECTIVES: Asthma is a major healthcare problem. Understanding current patterns of healthcare utilization is important. Several previous studies compared healthcare utilization and cost by severity and health insurance; however, they may not be applicable to Thailand. This study aimed to compare healthcare utilization and cost by asthma severity and type of health insurance in Thailand. METHODS: A retrospective study using an electronic database was conducted in patients with asthma who visited a University-affiliated hospital during 2009-2011. The outcomes were healthcare utilization and costs of in-patient and out-patient care. We compared outcomes between groups based on a proxy of severity (high vs. non-high risk of emergency department visit) and type of health insurance. Multivariable generalized linear regression model with log link function was used to determine the difference of average healthcare cost, while multivariable negative binomial regression model was used to determine difference of the number of hospitalization among groups of severity and health insurance. Costs were converted to $US using 30.59 Thai-baht per $1US. RESULTS: Among 1,982 patients included, the average age was 40.3±24.0 years with 60.7% male. A total of 1,936 patients were non-high risk patients, while 46 patients were high-risk patients. There were 1,293 patients under universal coverage schemes (UCS), 264 patients under social security schemes, and 626 patients under civil servant medical benefit schemes (CSMBS). The average annual cost/patient was $598±871. In adjusted analyses, the healthcare cost of high-risk patients was $67 higher than that of non-high risk patients (95% confidence interval (CI); $64–$69). The cost of patients under CSMBS was $109 (95%CI; $105-$113) higher than that of patients under UCS.   CONCLUSIONS: The healthcare costs in a cohort of patients with asthma were substantial and were higher in high-risk patients and patients under CSMBS.