The mixed-methods study addressed the needs and challenges faced by first-grade English teachers in rural primary schools in Southern Thailand (for example, lack of pedagogical training). The study’s primary objectives were to investigate these teachers’ needs and difficulties, develop a 15-hour online pedadgocial training course, and evaluate its effectiveness after the training was completed. The research involved 33 teachers and 153 students and employed various tools, including questionnaires, an online pedagogical training and language course, pre-and post-tests, and semi-structured interviews about the experience. The findings highlighted the importance of training in speaking, vocabulary, materials, games, and communicative language teaching (CLT) for these teachers. Statistically significant improvements (p < 0.001) were observed in post-test scores for both teachers and students, indicating the positive impact of the customized online training course on teachers’ English skills and teaching performance and improvement in student learning outcomes.