This was my experience when extending my retirement visa at Nong Khai Immigration yesterday:-

I presented the following documentation:-

1. Passport with all pages copied
2. Letter from bank confirming balance of bank account here, dated that same day.
3. Copy of bank passbook pages, updated that same day and showing that day's balance (I made a withdrawal beforehand to ensure it showed today's date). The required balance had been in the account over 3 months.
4. Visa extension application form
5. Photograph
6. Fee 1900 baht

7. I kept back my tabien bahn (house registration book), until it was requested. I then presented it with photocopies of the pages.

I was seen by Mr Happy, who barely spoke to me apart from when asking for things. He managed to extend the process by shuffling papers, discarding some unneeded passport copy pages, re-gluing his receipt book & re-checking the copies within, and processing things for his colleagues.

When it got to the fee paying point, I said I also wanted to apply for a re-entry permit, the form for which I had been completing whilst he was processing the visa extension. This added about 5 minutes to the procedure.

Final approval was given by the boss lady on the left. It took 30 minutes in total, and I was asked for 20 baht copy fee.

Thanks for the heads up and I', glad to hear it all (almost) went like clockwork Jaidee .