What is a Certification Letter from the US Embassy required to open a bank account in Thailand?

Same thing when I tried. They wanted a certified copy of my passport. The certification must be done at the US Embassy either in Bangkok or Chiang Mai trying to get an appointment in Bangkok was weeks away so my wife and I took a train ride up to Chiang Mai and got it done in one week. You have to make an appointment for a notary.  I know you mentioned a certification letter is what they were saying at the bank, but you may want to clarify and make sure is it a letter or a certified passport from the embassy there may have been miscommunication from the people at the bank.

Get a Letter of Residence at the Imigration. Picture + 500THB and try Bangkok Bank

They probably meant a residents certificate from your local immigration office, standard practice.

You need a certificate of residence

from immigration near the airport 500 bhat and more than 30 day visa try the Bangkok Bank opposite Chiang Mai Gate. I got mine there 2 months ago on visa exempt extantion

I opened a bank Accnt thru Bangkok Bank in Chang Mai . At the time I was staying in a condo for 3 months . The manager registered my stay @ the Immigration & I had a copy of the contract . I took that to the Immigration , got my letter of residence . I paid 500 baht and the next day I took that form to the bank .

The American Embassy will not give you any kind of letter for opening a bank account.

I opened a Bangkok bank account with passport and oa visa no problem,K bank next door refused as I didn’t work in Thailand,Krungthai bank refused as my visa wasn’t stamped in my passport,went to k bank in Khon Kaen which is our local big city and refused using my oa visa but because I am married to Thai national they said that was ok and gave me a bank account,it goes to show there’s no set criteria and basically it’s pot luck on the day.

Not from US embassy but from Thai immigration, I hope. That's what I'm doing

The Formal requirements to get a Residence certificat from the Immigration, is that you have been staying at least 3 month on a long stay visa.

that will be bangkok bank, they want you to get a document stamped at your embassy.

Try krungsri bank I found them easy process I got a ATM card and a bank book within 30 minutes

Probably meant you need to get a residency certificate from immigration. That is a requirement to open a bank account.

As far as I know you will need a certificate of residence from your local Immigration office.

Get a residence certificate from immigration.

Try a different bank.

Did you just go to one bank? Requirements actually differs between banks, even between branches. Bangkok Bank is considered the most foreigner friendly bank in Thailand. Fyi, the US Embassy has stopped issuing the equivalent to immigrations Residence Certificate.