METV as Ellie mentioned is probably the better option to do. So much paperwork and high insurance requirement, health medical check, police check etc. go with the easier METV and take a plane trip out then back in instead of jumping though all the STV requirement hoops.
You should be able to go in with the 1900 baht and your passport and don't forget that little square TM6 form that you got when entering Thailand though Immigration - hopefully you didnt lose it. You will also need a passport photo and photocopy of your passport page. There should be a photocopy shop nearby Immigration to do that at. Robert answered your accommodation question.
as I understand it you have done approximately 90 days with one standard extension already done. In which case the 60 day covid extension maybe your best option now.
Going on what happened last year before they extended the program, 30 September would be the last day you can get your last extension. People entering Thailand after the end of this month on this visa may not be able to get full 270 days as this date nears closer. People who entered this month will need to apply early for their 2nd extension.
Ask your condo owner to prepare you an updated condo agreement with new dates. This can be done electronically in PDF format which you can both sign if tech savvy. Don’t need pen and paper to sign these days
Today I received my 5 day test result back as not detected so I went to my hotel reception to ask about this certificate or equivalent since I was doing the sandbox in Phuket before flying onto Bangkok tomorrow. They were able to provide me this letter which I hope will meet the STV extension requirements. I will ask for a hotel receipt tomorrow before I leave to be sure as point 6 seems to ask for 2 pieces of paper.
I’m currently on STV in Phuket and just had my day 5 test and waiting for result. I will be requiring this type of document as I will move to Bangkok next week. I will ask my hotel as soon as I receive my test result back about the certificate.