Online learning is readily available in Thailand, and scholars acknowledge its importance in assisting language learners to accomplish their foreign language goals. Currently, with the COVID-19 global pandemic, self-distancing is helping to reduce the infection rate. Since learning must continue, technologies play a vital role. Educators and students have managed to adjust to the unprecedented situation and continue with classes despite the many obstacles. Thus, this study examines the characteristic variables (motivation, belief in language, and anxiety) and self-regulation in online English learning classes, as well as investigating the relationship between the characteristic variables and self-regulation of undergraduate students at a private university in Thailand. The study involves 132 participants enrolled in an online English course during the pandemic, with a questionnaire and focus group interviews employed as the research instruments. The results showed that the students were highly motivated, exhibited positive beliefs, moderate anxiety, and high self-regulation toward online English learning. Two variables, namely motivation and positive beliefs, were found to be correlated with self-regulation in online English learning at the 0.01 and 0.05 significance level, respectively. Anxiety in online English learning was found to have no significant relationship with self-regulation in online English learning, indicating that students experiencing some level of anxiety during the online class could still exhibit self-regulated behavior. These findings are expected to provide a foundation for further research in the online learning field.