The research from 1991 to 2021 compares human development progress in Indonesia and Thailand while analyzing factors influencing their Human Development Index (HDI). The study uncovers significant disparities by employing independent difference tests and Autoregressive Distributed Lag. Indonesia exhibits rapid economic growth yet faces health and educational inequalities. Thailand boasts a higher average HDI (0.70) than Indonesia's (0.63), signaling pronounced developmental gaps. ARDL analysis identifies distinct factors shaping HDI in each nation. Long-term impacts in Indonesia stem from increased life expectancy and education, while Thailand benefits from GDP and investment. Short-term effects reveal Indonesia's positive response to previous GDP changes, while Thailand experiences initial negativity but long-term positivity. Policy recommendations stress Indonesia's need to enhance investment, economic growth, health access, and education quality to narrow the HDI gap. Equitable wealth distribution and heightened investments in health and education are pivotal for achieving inclusive and sustainable human development.