Paul what you write seems like a practical solution. Try it in real life. Pay 5000bht to agent problem solved if you have a 12 month lease or yellow book.
I tried many small branches on advice without success. One branch told me to marry Thai lady to open account. Ended up using Laurie, Chiang Mai visa shop with no problems and now have retirement visa.
Maybe ears blocked caused by flight. This has happened to me either go to doctors or hospital for check. I needed wax removed from ear, after removal all good.