Thailand is among the first non-OECD countries to have introduced a form of Universal Health Coverage (UHC). This policy represents a natural experiment to evaluate the effects of public health insurance on health behaviours. In this paper, we examine the impact of Thailand’s UHC programme on preventive activities, unhealthy or risky behaviours and health care consumption using data from the Thai Health and Welfare Survey. We use doubly robust estimators that combine propensity scores and linear regressions to estimate differences-in-differences (DD) and differences-in-DD models. Our results offer important insights. First, UHC increases individuals’ likelihood of having an annual check-up, especially among women. Regarding health care consumption, we observe that UHC increases hospital admissions by over 2% and increases outpatient visits by 13%. However, there is no evidence that UHC leads to an increase in unhealthy behaviours or a reduction of preventive efforts. In other words, we find no evidence of ex ante moral hazard. Overall, these findings suggest positive health impacts among the Thai population covered by UHC.