This study aims to assess the impact of online tutoring on oral English fluency in Thai adult learners who have had only primary education in their native language but have no formal education in English. The research involved 34 adult learners participating in online hourly tutoring sessions over six months. Pre- and post-tests were used to measure oral fluency progression, and structured interviews were conducted to understand learners' experiences and strategies. The results indicate a significant enhancement (p < 0.05) in oral fluency, with learners progressing from beginner to independent user levels on the CEFR Global Scale. While the majority exhibited substantial improvement, a subset showed moderate progress. Qualitative insights from interviews highlighted effective learning strategies employed by the participants. This research emphasizes the potential of online tutoring as an effective approach for non-native adult English learners, particularly those lacking formal education or print literacy. The findings offer valuable insights for designing and implementing language learning programmes, emphasizing the importance of learner commitment and motivation. This study is a practical guide for similar learner populations, offering implications for future language learning initiatives.