Background <p>Despite Thailand’s universal healthcare coverage, socioeconomic and geographic disparities in dental care utilization persist, particularly among older adults. This study examined the patterns and determinants of inequality in dental care use among older adults in Thailand (aged 60 and above) during the country’s transition to an ageing society (2009–2021).</p> Methods <p>Nationally representative data from the Thailand Health and Welfare Survey (2009, 2015, 2021) were analyzed (<i>N</i> = 53,825 older adults). Dental care utilization was assessed via self-reported use in the past 12 months. Weighted analyses and multivariable logistic regression were performed to examine associations between dental care utilization and socioeconomic, geographic, and health-related factors, classified according to the Andersen Behavioral Model of Health Services Use.</p> Results <p>Overall dental care utilization among older adults declined from 9.1% in 2009 to 7.2% in 2021, despite near-universal health insurance coverage. Substantial socioeconomic and geographic inequalities in dental care utilization were observed across all survey years. In 2021, after adjustment for covariates, respondents in the highest household asset quartile had significantly greater odds of utilizing dental care than those in the lowest quartile (adjusted odds ratio [aOR] = 2.4; 95% confidence interval [95% CI]: 2.0–2.9). Older adults with tertiary education demonstrated markedly higher odds of utilization compared with those with no formal education (aOR = 6.0; 95% CI: 4.3–8.3). Geographic disparities were also evident, with older adults residing in the Northeast showing substantially lower odds of utilization than Bangkok residents (aOR = 0.3; 95% CI: 0.2–0.3). Beneficiaries of the Civil Servant Medical Benefit Scheme (CSMBS) had higher odds of dental care utilization than those enrolled in the Universal Coverage Scheme (UCS) (aOR = 2.0; 95% CI: 1.8–2.3).</p> Conclusions <p>Despite Thailand’s long-standing near-universal health coverage, substantial inequalities in dental care utilization persist among Thai older adults, particularly among socioeconomically disadvantaged and rural populations. These findings suggest that equitable oral healthcare in ageing societies requires policy approaches that extend beyond financial coverage alone and address structural, geographic, and ageing-related barriers to care. Strengthening community-based and geriatric-sensitive oral healthcare delivery may help reduce persistent inequalities in access.</p>