Water policy decision-making is hindered by limited involvement and understanding of the issues by the affected community members. This study demonstrates that implementing a serious game concept to explain Strategic Environmental Assessment (SEA) can improve a community’s knowledge and skill in water policy decision-making. The authors developed a tool called SEA Game and Simulation using the MIT App Inventor and participatory techniques. The developed tool was implemented among 39 community members in the East Coast River Basin of Thailand. Key findings indicated a significant improvement in the participants’ knowledge of SEA and skill in water policy decision-making. Results from implementing the tool were dependent on the background of the participants and the context of the events. Further studies related to developing sustainable measures from SEA in community sectors should be considered.