You should mention this to banking authorities in the US. They are paranoid about money-laundering and thai banks hates it. They don't like the extra paperwork, mainly because of FATCA.
I'm retired and I've been living in Thailand many years. I'm not the least interested in saving money for re-entry permits. I'm paying ฿19k for 10 years. Imo,money well spent. On top of that,I'm in walking distance from Jomtien immigration. Every 90 days report takes maybe 1 minute where I hand over what they want, and I pick up my passport next morning during my morning walk. Does this sound time-consuming in your universe? The LTR-visa is imo just a waste of money if you're supposed to retire full time in Thailand.
If you meet the financial requirements for a common retirement visa, there's no need for an agent. The process is quite straight forward.The LTR-visa is imo, just a waste of money.
Bangkok Bank, and yes, you need 30 days plus to be able to open a savings account there. I guess you mean the bank letter for the 1 year extension. Most immigration offices accepts copies from an updated bank book when using the "money in the bank-method". Meaning, no need for a bank statement.