Bangkok bank can issue 3 letters. One is called a credit advice, all in English with sender name, ordering institution and address in your country, other letter will be in Thai verifying money recieved from aboard. The last letter stating your latest 800K balance.
Go where your lastest extension was issued/ renewed/ stamped. IO has to verify in handwriting whose signature it was under the original stamp. So only that office knows who signed.
Request a wheel chair from the check in counter. Tell them your legs hurt. You will get wheelchairs and the services at all stop. You just tip a 100 B to the Thai helper. He will proceed you thru the fast lane.
Unlike tourist visa in Europe, you can enter Thailand on the last day of your visa (stamps, stickers, or evisa print outs) and still get another 60 days from the date you enter. Tourist visa in Europe starts and ends on the date shown in the visa itself.