Prachumchai, S. ., and H. . Anghirun. “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, vol. 3, no. 2, July 2020, pp. 273-86, https://so04.tci-thaijo.org/index.php/jmhs1_s/article/view/243719.