The One Health, One World Organization (OHOW) held The 1st International Symposium on One Health, One World in Pattaya, Thailand from December 8 to 10, 2022. "One Health, One World," proposed as the Manhattan Declaration in 2004, is recognized as a comprehensive scientific concept that encompasses human and animal health, the global environment, urban safety, and urban environmental management. This symposium was organized by the Regional Office for Urban Safety (RNUS), which was established at the Asian Institute of Technology (AIT) in 2002 to improve urban disaster prevention in the Asian region and to build a human network for the purpose, and has continued for 20 years. OHOW took over the International Symposium on New Technologies for Urban Safety of Mega Cities in Asia (USMCA), which had been held for 20 years. The three-day symposium featured six keynote speeches and 76 research presentations on such topics as natural disasters and infectious diseases, transportation and human mobility, structural and geotechnical engineering for human safety, infrastructure health monitoring, public health and climate change, and ecosystem monitoring using remote sensing and GIS. There were 101 participants from 15 countries including Japan, Thailand, Nepal, India, Bangladesh, Myanmar, Indonesia, Cambodia, Philippines, Vietnam, China, Pakistan, Iran, Sweden, and New Zealand. Among 44 presentations by young researchers and students, four were awarded as the best presenters. It was the first time in three years since the 19th USMCA that the conference was held face-to-face, providing an opportunity to reunite with old acquaintances and meet researchers in new fields, while at the same time providing a meaningful discussion for the comprehensive and coordinated development of related academic fields to address the various risks facing society from human, animal and global environments that OHOW targets. The second meeting is scheduled to be held in Dhaka, Bangladesh, in December 2023.