This study analyzed health care utilization of Thai people who did not have or were not aware of health insurance, using data from Health and Welfare Survey 2015. Demographic, socio-economic characteristics plus utilization patterns of outpatient (OP) and inpatient (IP) services were analyzed. Out of pocket payment was reported as the median amount. The results showed that 1.49% of Thai population neither had health insurance nor knew their status. Majority (38%) lived in Bangkok while 17% and 12% lived in Health Region 5 and 6, respectively. Approximately 51% were male and aged 30 years on average. Sixty-five percent completed up to the primary schools and 41% were private employees. With respect to economic gradients as measured by household asset index, the poorest quintile had a greater proportion of the primary school graduates and private employees than the rest. Of all Thai population, ten percent reported having non-hospitalized illnesses (outpatient, OP) during one month and mainly received care at private hospitals (37%) and clinics followed by drug stores or traditional healers, and public hospitals. Median paid amounts for the above OP services were 350, 80, and 2,300 baht per visit, respectively. The poorest quintile used drug stores in the largest proportion, followed by private and public facilities, and paid for a visit of 80, 300, and 200 baht, respectively. The richest quintile used private facilities the most, followed by public facilities, and drug stores. There were only four percent reporting being hospitalized during the past year, which was not different across economic quintiles. Approximately, 70% of those hospitalized were admitted to public hospitals. All people in the poorest quintile were hospitalized in the public hospitals and paid 8,000 baht per admission, while 69% of the richest quintile were hospitalized in the private hospitals and paid 40,000 baht per admission. To mitigate financial risks to health payments by households, especially among the poor, and strategies for identifying the Thai population who did not get access to the UCS registration are thekey priority issues, especially in the urban areas and big cities.