The flipped classroom instructional approach gained popularity after the COVID-19 pandemic, which significantly disrupted language instruction. This study aimed to evaluate the effectiveness of a full online flipped classroom instructional model to enhance students' meeting skills and their engagement. The model consisted of two lessons: group meeting skills and writing the minutes of meetings. The participants comprised 48 third-year undergraduate engineering students from a public university in Thailand. The study utilized the KW#4 principle to compare average scores of passing students in formative and summative assessments, and to analyze pre-test and post-test scores, aiming to evaluate the model's impact on students' meeting skills. Student engagement (affective, behavioral, and cognitive) was examined using a questionnaire and semi-structured interviews. The results showed that the model was effective, as the post-test scores were significantly higher than the pre-test scores. Further, the results from the KW#4 revealed that the model was effective since the effectiveness of criterion learning (formative and summative tests' average percentage) in using the flipped classroom to enhance group meetings and the minutes of the meetings of the students was 87.6/82.8 and 74.06/74.02, which was higher than that of the set standard criteria of 60/60. The students also demonstrated a high level of positive cognitive, behavioral, and affective engagement. The study provides a holistic perspective on the effectiveness and practicality of the model, thus yielding further support for technology-integrated language instruction in ESP courses.