Can I extend my NON-O visa date if I will be out of Thailand before it expires?

When are you exiting?

You should have asked Immigration yesterday not accept it then come to ask here as nobody here can help

All you can do is go back to your local office with the fixed tickets (that can prove you are out of Thailand) to discuss the timeline.

If they can amend the date, follow their directions.

If they say, no, it's too late to change the date, you may have to start the whole process over from the initial visa again.

To all,

If you have any slight possibility of travelling abroad during the under-consideration period, don't forget to mention your travel schedule when (and just before) you submit your application documents. It makes things much easier.