What are the options for an American spouse on a Non O Visa wanting to open a bank account and extend their stay in Thailand?

This group is neither banking advice or for the process on how to get a marriage registered within Thailand. Different amphurs have different requirements for getting a marriage certified inside Thailand.

For the best banks to use, ask on a Facebook group that's local to where you live.

For getting a foreign marriage legalized, ask the local Amphur office.

To register yer marriage at local district office and to get 1 yr extension u will still need to get yer marriage cert notarized by the Embassy and then translated, then both must be stamped by Thai Ministry of Foreign Affairs. Same must be done for data page of yer passport and a Embassy affidavit that states that you guys are married. Then all is taken to local Amphur to be registered. After that and with lots more paperwork, u can apply for the 1 yr Extension.

Try to stick with the big three banks, Bangkok Bank, Kasikorn, or Siam Commercial Bank.

> We are planning on staying here for 4 and a half months.

If you entered on a single entry Non-O visa based on marriage to a Thai national, you will have entered for 90 days. You can get ONE 60 day extension of stay based on visiting Thai family at the local immigration office. You may need to get your marriage registered at the local Amphur office.

A 60 day extension of stay based on visiting Thai family does not require any proof of finances 🙂

>I had planned on getting a 12 month extension and a reentry permit and coming back here again in November of this year.

As Lloyd mentioned above, opening a bank account does not require proof of marriage. Take your wife with you, and start going to various banks around town. The first bank you will go to will probably not allow you to open the account, and you'll have to keep on trying different banks.

Bring your passport, and a rental agreement (if you're renting). If your immigration office allows a residency certificate to be issued before submitting a 90 day report, get an residency certificate and use that.

You are opening a bank account in your name only, absolutely no need to register a marriage.