Preepul, D. ., P. D. . Vajirapanyo, and S. . Bamrungphak. “The Development of Ethics of Professional Teachers under the Office of Kalasin Primary Education Service Area I”. Journal of Graduate MCU KhonKaen Campus, vol. 6, no. 4, Dec. 2019, pp. 97-108, https://so02.tci-thaijo.org/index.php/jg-mcukk/article/view/230142.