I recently got my 1 year extension in Bangkok. There are many bank branches at that immigration office. The immigration officer told me what she needed from the bank. The banks there know what letter you will need for immigration. They will update your bank book. I withdrew 1000 baht the day I was there before updating my bank book. This info is just for the Bangkok immigration office.
The visa and the re-entry permit are two different things with two different prices. All I learned about visas I learned from Tod Daniels. He is the final word on all thing visas. Or at least he is one of a few experts moderating this group.
After my first year I purchased a multiple re-entry permit but it expired on the same date as my last stamp in my passport. I only got 9 months use. Now with my 1 year extension I will get the full year of my new multiple re-entry permit.
I arrived in February 2017. I made three trips to the US and a final trip to Cambodia in Nov 2017. I was stamped in until November 2018. I recently got my first 1 year extension.
I just got my year extension in Bangkok. I could meet both the income requirement and the bank requirement. If someone else can do the same then they could try meeting the income requirement with bank statements. If that doesn’t work then they have the bank deposit as a backup.