Charoontham, Orasa. 2020. “The Effect of the Instruction by Project Based Learning (PBL) on the Student’s Achievement in Science Subject and Problem-Solving Ability of Secondary School Students”. Journal of Research and Development Institute Rajabhat Maha Sarakham University 7 (1):225-40. https://so03.tci-thaijo.org/index.php/rdirmu/article/view/245101.