This study explored the learner autonomy of Thai EFL undergraduates in English language learning and the extent to which they conducted learner-learner interaction, learnerinstructor interaction, learner-content interaction, and overall interaction. Moreover, the study investigated whether there was a significant difference in overall interaction for different learner autonomy levels. The sample included 83 English major freshmen enrolling in an online English Phonetics course at a public university in Bangkok, Thailand. The data were collected through an online learner autonomy and interaction questionnaire. Descriptive statistics, one-way ANOVA, and post-hoc Tukey tests were utilized to analyze the data. The findings revealed that the participants possessed a high level of overall learner autonomy. While they had a high level of ability to learn English autonomously, they had a moderate level of responsibility for their learning process. Further, the participants had a high level of overall interaction. Although they had a high level of learner-content and learner-instructor interaction, they possessed an average level of learner-learner interaction. The participants with a low learner autonomy level had significantly lower overall interaction scores than those with a moderate or high level of learner autonomy.