The purposes of this research were to study and compare knowledge about Khok Hin Lad community forest, environmental ethics, and environmental volunteers from learning activities of undergraduate students before and after activities, to study and compare knowledge about Khok Hin Lad community forest, environmental ethics, and environmental volunteers of undergraduate students with different gender and GPAs. The sample used in the research was 99 second-year undergraduate students in Environmental Education, Faculty of Environment and Resource Studies, Mahasarakham University, which are derived from purposive sampling. The research instruments were a manual of environmental learning activities in Khok Hin Lad community forest by using area-based learning, knowledge test about Khok Hin Lad Community Forest, Environmental ethics test, and environmental volunteers test. The statistics used in the research were frequency, percentage, mean, standard deviation. And hypothesis testing using t-test, F-test (One – Way MANOVA, One – Way MANCOVA, and Univariate Test). The study found that: 1) The student's knowledge average score of Khok Hin Lad community forest, environmental ethics, and environmental volunteers after learning activities were higher than before the learning activities' statistical significance (p< .05). 2) There was no different knowledge of Khok Hin Lad community forest, environmental ethics, and environmental volunteers between students of different gender (p> .05). 3) There was no different knowledge of Khok Hin Lad community forest, environmental ethics, and environmental volunteers between students with different GPAs (p>. 05).