Also bear in mind that Pattaya immigration often like to make a home visit during the consideration period, so make sure you advise them of your availability.

You can apply on 10th September (1 month b4 expiry). In my experience they won't consider doing it any earlier in Pattaya unless you can show good reason. The consideration period is normally 1 month approx then you should go to pick it up. Again, if you can show good reason, they can amend this period to suit at their discretion.

Alternatively you could consider doing the application at the very end of September b4 travelling abroad in which case the consideration period date would likely be end of October. Obviously you would need a re entry permit, and would need to re enter Thailand by this date stamped on passport. Good luck!