Chantahong, Metawalai, Prapatsorn Pree-iam, and Arun Suikraduang. 2021. “The Development The Development of Problem-Based Learning Activities on Price Mechanisms in the Economy Economics Secondary for Grade 9”. Journal of Research and Development Institute Rajabhat Maha Sarakham University 8 (2):327-40. https://so03.tci-thaijo.org/index.php/rdirmu/article/view/252170.