This study investigates the factors influencing the usage behavior of online learning platforms (OLPs) among learners in Southeast Asia by employing the Unified Theory of Acceptance and Use of Technology (UTAUT) mode. By utilizing UTAUT, the study aims to understand how learners' Behavioral Intention (BI), System Facilitating Conditions (SYFC), and Service System Facilitating Conditions (SEFC) impact their Usage Behavior (UB), taking into account the region's diverse cultural and social characteristics. Using a mixed-methods research design, the study collected qualitative and quantitative data from 653 respondents across eight Southeast Asian countries. Findings indicate that PE and SI significantly predict learners' intention to use OLPs, while SYFC and SEFC influences usage duration, payment behavior, and platform recommendations. Variations in learning behaviors are observed between learners focused on certification and those driven by personal interest. Results of the study contribute valuable insights for OLP providers, educators, and policymakers, offering theoretical and practical recommendations for tailoring OLP products to the Southeast Asian market's specific needs. Research limitations include sample representativeness and potential biases in self-reported data. Future studies should address these limitations and further explore regional variations in OLP usage patterns.