Do I need to cancel my Non-B extension before leaving Thailand, or will it expire automatically?

If you have a Non-B 1-year extension expiring soon and plan to apply for a different visa from outside Thailand, simply leaving the country will not officially cancel the extension. It's advised to visit immigration and formally cancel the extension to avoid complications in the future, especially if you plan to work or apply for a long-term visa again. Additionally, ensure that any associated work permit is also canceled.