Do I need to reapply for a Non-Immigrant O visa each time I leave Thailand if I plan to travel around Asia?

The Non-Immigrant O visa for visiting family is indeed a single-entry visa, meaning you would have to apply for a new visa each time you leave Thailand if you do not have a re-entry permit. For frequent travel around Asia, consider obtaining a yearly extension after your initial entry, which allows for multiple re-entries throughout the year. Alternatively, entering Thailand on a visa exemption allows you to stay for 30 days, with the possibility of leaving and returning from another country; however, you must adhere to the exemption rules.