Kantatong W. The Development of a Model for Volunteer Spirit of The Lower Secondary Level Student in Opportunity Expansion School in Thailand. J.Humanities Social Sciences [internet]. 2023 Feb. 16 [cited 2026 Sep. 12];6(1):234-45. available from: https://so04.tci-thaijo.org/index.php/jmhs1_s/article/view/261984