Thailand has had remarkable successes in its universal health coverage (UHC) policy and health development. Thailand has also eliminated maternal-to-child transmission of HIV, and is the first country with a generalized HIV epidemic to reach this milestone. Since the Declaration of Alma-Ata in 1978, the design of primary health care (PHC) in Thailand has evolved significantly in response to the population’s evolving health needs. The capacity of successive governments to respond to health transitions and engage the community has shaped the design of Thailand’s PHC. This commentary reviews the historical evolution of PHC in Thailand, its contribution to securing the favourable outcomes of UHC, and the ongoing adjustments required to make it fit for the future.