sorry found similar post

Edited January 26, 200917 yr by tom21

I have a non imm O with a 12 month extension. I am planning on going home (Australia) for 2 months later this year. The extension will expire just before I return to Thailand so just wondering what the best thing to do.

Actually your extension will expire the day you leave Thailand.

Immigration may accept an application for another 12 months extension. If they do you will require a Re Entry Permit to keep your extension date alive.

Or when you get back to Thailand you can start all over again.

You could check with your local immigration office before you leave to see if they will do your extension early.

If not then it's either be here before your permit to stay ends. Or start all over by getting a non-o visa before you leave Australia and then apply for a new extenssion at immigration after you get back.