Misinformation affects people because it can convince them to believe in how to respond to uncertain situations. During the COVID-19 pandemic, a number of misinformation or fake news were distributed on social media, in Thailand. This research aimed to study attributes and causes of Health-Related Misinformation Sharing in Thailand on social media during the COVID-19 pandemic. Dataset used in this study was collected from the Anti-Fake News Center, the Thai government factchecking website certified by the International Fact-Checking Network (IFCN). In-depth interviews based on qualitative research technique were also conducted to identify the causes of the transmission of false health news on Thai social media by applying the rumors transmission concept during times of crisis and the theory of Uses and Gratifications. The findings showed five main themes of fake news: conspiracy theories, pseudoscience, fake advertisements, inaccurate information, and misleading information. These elements may establish a conceptual framework for finding the root cause of misinformation spreads during crises. Factors that affect how psychological information was presented and shared are anxiety, insecurity, and uncertainty during the crisis. However, belief is not the only justification for sharing this information because some social media users have shared unverified and no evidence information for personal purposes. The Uses and Gratifications theories are found relevant. This study is intended to broaden the reach of disseminating misleading information as much as possible to lessen the effect of detrimental health fake news on Internet news consumers.