This study developed an online health education program by applying the Health Belief Model with social support to prevent tobacco use by student teachers and evaluated the effectiveness of the program during the COVID-19 pandemic in Thailand. This involved mixed method research divided into 2 phases, with phase 1 combining an online focus group discussion (n=8) and a literature review to develop an online health education program to prevent tobacco use, while phase 2 involved evaluating the effectiveness of the program. Phase 2 used a randomized pretest-posttest control group design consisting of an intervention group (n=30) and a control group (n=30) selected by simple random sampling for both groups from student teachers in academic years 1–5 in the Faculty of Education, Kasetsart University, Bangkok, Thailand. The result from phase 1 for the proposed program for the intervention group involved 8 weeks of online activities, including exercise, meditation, music, games and lectures by experts in public health, health education, and experiences shared by ex-smokers. Leaflets were provided to all participants in both the intervention and control groups. The results from phase 2 showed significant differences in knowledge (p < 0.000; p < 0.007), attitude (p < 0.000; p < 0.034) and risk behavior to tobacco use (p < 0.004; p < 0.025) for both the intervention and control groups at 8 weeks post-intervention compared to pre-intervention, respectively. The program could support, guidance, and contributions of the many individuals and organizations that have been involved in the online process.