Why not let it expire and apply for another 90 day non o before you return to Thailand? In other words, start again. I assume you have the financial requirements banked already.
when you are sitting at immigration getting your 12 month extension stamp, if they do not put a notification to you to keep in your passport just ask them.
It's not called a 90 day report for nothing. 90 consecutive days within Thailand unless you get an extension in which case immigration will give you notification of when it is due.
My office require statements dated on the day of application. The statement and bank book also need to show a transaction on the day. I usually do a phone top up in the bank. Its not a bad idea to ask your office to write down in thai exactly what they require.
Others have advised on Visa. Try earlier. Talk to them and try and work something out. I had TIA in 2015 and after haggling they insured me but with a 1 year moritorium for anything heart related. I am now full covered.