My Re-Entry Permit & permission to stay (basis of marriage) expire on Monday 5th August 2013.

However, when I lodged my application for a further 1 year extension on 9th July, the Immigration Officer at Chaeng Wattana stamped the following:

"Application for extension of stay is under consideration of the police department. Applicant must contact the temporary permit section in person on 6th August 2013."

On that basis it appears that I may incur an overstay of 1 day (5th Aug vs 6th Aug).

Therefore, should I go to Chaeng Wattana on Monday 5th August instead of Tues 6th August?

You will not be on overstay. You are allowed to remain in the country until the 6th or even longer as long as your application is still under consideration.

Thank for your prompt response UbonJoe, which makes sense.

A colleague in my office had advised that I may have an issue because I left the country for 2 days during the '30 day under consideration' period, and that I should have obtained a new Re-Entry Permit for that short trip otherwise my 'extension of stay' will be voided. When I re-entered the Kingdom last week after the 2 day business trip overseas, the Immigration Officer at Surnabhumi Airport stamped by passport with "Admitted until 5th August", i.e., in line with my existing Re-Entry Permit expiry date (as expected).

I hadn't previously heard that if you travel abroad during the '30 day under consideration' period you would require a new re-entry permit. However, after my colleague mentioned this to me, I pressed the panic button, hence this posting on TV.

Indeed you are likely now legal only until the 5th but expect immigration may be understanding. Yes you should have obtained a new re-entry permit when you get a new permitted to stay stamp but in your case it is so close likely to not even be noticed.

I hope it all works out OK for you but I would prepared for the worst meaning immigration makes you do another application to start the process all over again. Or at the very worst tells you need to get a new visa and start all over again.

I went to Chaeng Wattana today & was happy to receive my new 12 mth extension of stay stamp and a new re-entry permit without any problems.