Samitsomboon, Mattika. “A STUDY OF SELF-DISCIPLINE OF VOCATIONAL CERTIFICATE STUDENTS IN PRE-ENGINEERING COURSE”. Research Community and Social Development Journal 17, no. 2 (June 28, 2023): 180–190. accessed September 17, 2026. https://so04.tci-thaijo.org/index.php/NRRU/article/view/265272.