COVID-19 has transformed how teaching is organized, with computer-mediated communication (CMC) implemented to overcome physical constraints from social distancing. This study explored behaviors and approaches employed by 10 English teachers from three private schools to optimize ELT with CMC in southern Thai provinces. Data collection involved focus group discussions and semi-structured interviews with the participants. Findings revealed that the students had transformed their behaviors of learning English through CMC. Consequently, CMC was utilized in two ways, including as auxiliary and primary instruments. Firstly, CMC was employed to supplement synchronous learning in the early stages of COVID-19 with social media to assign and return completed tasks. Nevertheless, online classes saw low student participation, notable learning fatigue, limited English practice opportunities, and inadequate self-practicing for language development. Secondly, after CMC was utilized as a primary instrument; the students had a broader opportunity to study English; demonstrated a higher commitment to learning; and adopted autonomous learning, self-assessment, and digital skills. This study further found that CMC-ELT performance could be maximized by allowing students to actively design their online learning, using diverse applications to promote participation, introducing creative content to reduce limitations, increasing spaces for autonomous learning, and providing channels for publishing student outcomes.