Esichaikul, R. ., R. . Chansawang, C. Songsoonthornwong, and Y. . Kaewudom. “The Study and Revision of the Tourist Guide and Tour Leader Training Courses”. University of the Thai Chamber of Commerce Journal Humanities and Social Sciences, vol. 40, no. 2, June 2020, pp. 1-30, https://so06.tci-thaijo.org/index.php/utccjournalhs/article/view/224478.