Prachumchai, Sapolachet, and Hathaichanok Anghirun. 2020. “The Jolly Phonics Camp to Enhance Lower Elementary Students’ English Pronunciation at the Highland Schools in Phetchabun Province”. Journal of Multidisciplinary in Humanities and Social Sciences 3 (2):273-86. https://so04.tci-thaijo.org/index.php/jmhs1_s/article/view/243719.