What are the steps and considerations for applying for a long-term married visa in Thailand as an expat with a Thai spouse?

Looking to get some constructive advice.. whilst sharing my experience to date.. i'm a British passport holder aged 60-yrs with a Thai wife.. living together in Chiang Mai with blue book in wife's name.. i arrived on 4-Mar by plane from Uk.. on a 45-day tourist visa expiring 17-Apr.. extended once by 30-days at CM Immigration to 17-May.. denied 60-day extension because an official marriage certificate translation (into Thai) hadnt been completed.. we subsequently engaged an agent to attend to this and this document is now available to support future visa applications.. the marriage has since been registered with our local Amphur District Office and a certificate of residence obtained from them.. which evidences the marital home as my official address in Thailand.. i have also been awaiting a letter of consent to open a bank account from CM Immigration.. something Bangkok bank had insisted upon seeing before they would entertain it.. this document also recognises and certifies my residential status.. but the Amphur certificate was deemed insufficient for the bank's purpose in isolation.. the Immigration letter finally arrived in the mail today.. exactly 27-days after i had requested and paid for it.. which was the exact date they said i would get it when i attended CM Immigration on 24-Mar.. no explanation was provided when i queried the 4-week turnaround for such an in person application.. it was simply the standard processing time (apparently) and could not be expedited.. which i still cant fathom.. indeed, this process has only served to erode my visa clock.. by delaying my ability to get my funds on deposit.. then today when i went running to the bank i was blindsided when they turned me away.. because i didn't have a 30-day stamp (ie. unexpired visa) left on my passport.. so despite presenting all the necessary documentation they had previously demanded they decided to add a new (surely absurd) requirement to the checklist.. though i finally succeeded in my quest by visiting a larger branch who didn't once query my visa stamp.. so job done finally with the bank account.. however my intention is to seek a long term married visa.. ie. a 12-month multiple entry visa basis.. but my issues now revolve around the timing of this application and my ability to travel while this is being processed.. i need to travel to Singapore at the month end to attend my step-daughters graduation ceremony.. i intend to fly back to CM about a week later (around 8-9 May) but i'm concerned that my existing 'official' documentation.. such as the Amphur registration or Immigration certificate of residence will be invalidated by this trip.. thereby requiring a duplication of this effort.. furthermore can i apply for the married visa now with a view to it being issued once my funds have been on deposit for 60-days.. or can the application only go in once that 60-day hurdle has passed.. and if i'm able to submit the application now (persay) can i still travel without prejudicing my application.. or am i expected to stay in Thailand until the application is approved.. or should i apply for a different visa before i go to SG that will give me enough time to meet all requirements upon my return.. ie. without having to do a border run later.. you'll appreciate that i want to get all my ducks in a row so i follow the smoothest path possible.. whilst minimising the plethora of fees you have to pay along the way.. thankful to receive your thoughts and any guidance from the knowledge base here 🤔