I am on an extension of ED visa. The current extension expires in April. I will be abroad for 4 months, starting in March. Is the best thing to do cancel the extension before I leave? It is correct that it is not possible to just come back and re-extend it within Thailand?
TLDR : Answer Summary
If you are on an extension of an ED visa that expires in April and plan to be abroad for 4 months starting in March, it is advisable to cancel your extension before leaving Thailand. Upon returning, you will need to apply for a new visa, as it is not possible to re-extend your current visa while you are outside Thailand.