This paper explores HIV/AIDS stigma in the socio-cultural context of Nakhon Ratchasima Province in the northeastern region of Thailand. Action research was used to develop a community participation intervention. The intervention was implemented in one village over a period of eight months. We describe the intervention and then test its effect on HIV/AIDS knowledge and HIV/AIDS stigma using a non-equivalent pre-test-post-test control group design. Analysis of co-variance confirms that, controlling for initial levels of HIV/AIDS knowledge and stigma, the intervention had a significant effect on HIV/AIDS knowledge score (p<0.01) and HIV/AIDS stigma score (p<0.01). Participatory observations by the researchers on villagers' perceptions and behaviour were consistent with the quantitative results. These results suggest that community interventions which empower the community, combined with a financial contribution to reduce resource constraints, are a useful and effective means of increasing interaction between people living with HIV/AIDS (PLWHA) and other community members, increasing tolerance and reducing HIV/AIDS stigma.