The COVID-19 pandemic has affected all areas of life, including mass-gathering sport events like trail running. However, trail races are beginning to return across the world, including Thailand. Previous edition of Thailand by UTMB® on October 2020, was organized successfully during the Thailand border-closing period, implemented the guideline to organize running event during COVID-19 outbreak published by Ministry of Tourism and Sports. ITRA COVID-19 Guidelines were also benchmarked. Public health and related authorities have visited the event for assessment. For the next edition of Thailand by UTMB® on October 2021, after most of the trail runners were vaccinated, the organization will continue to implement best practices to minimize all the risk. Protective measures against the spread of COVID-19 will be announced to all participation.