Kladchuen, R. and Srisomphan, J. 2021. The Synthesis of a Model of Problem-Based Learning With the Gamification Concept to Enhance the Problem-Solving Skills for High Vocational Certificate. International Journal of Emerging Technologies in Learning (iJET). 16, 14 (Jul. 2021), pp. 4–21. DOI:https://doi.org/10.3991/ijet.v16i14.20439.