This study assesses the trend and prevalence of unmet healthcare need for outpatient, inpatient and dental services in Thailand between 2011 and 2019. The study also identifies reasons of unmet needs and population groups who had unmet needs. Findings indicate that the prevalence of unmet need for health services overall was low, remaining below 3% during 2011 and 2019. It was lower than OECD average (28%). The poor, the older persons, and people living in urban areas had higher unmet needs than their counterparts. The main reason for unmet need was long waiting times. The study recommends regular monitoring of unmet need through a national household survey to estimate annual prevalence and identify the causes of unmet needs, guiding policies to maintain and enhance access for specific population groups.