How do I apply for a marriage visa in Thailand if I need to leave and re-enter due to time constraints?

there's no rules against it, just you might spend days searching for one that will. a visa agent can assist you, maybe 90 minutes more or less of your time.

No rules on opening bank accounts have changed. Just keep trying different branches/banks or pay an agent.

I came 3 weeks ago on a non o visa and went to my local kasikorn branch and opened it no problem? They are the easiest

You can apply for the marriage visa online. Then leave/come-back and you will be on the marriage visa.

When filling out the application the first page will ask you something like "Where are you?" and "What is your nationality?", in both cases indicate USA. (this is not the actual application).

When you get into the actual application it will ask you the same question a little differently, "Where is your permanent residence" and " what is your nationality". For permanent residence, indicate USA and use your driver's license as proof. For nationality, obviously use your passport.

You will still have to show travel to Thailand. In your case I would buy a plane ticket to/from Singapore or whatever is cheap. And use that as proof.

You can not activate the visa until you enter Thailand. Because you are already in Thailand you will need to leave. You can take the plane you just purchased tickets for, or you can come/go however you want.

This approach has risks but it's worked out for me so far.

Also, during the visa process, they'll probably ask for some supporting documents, when you provide those, explain your situation, that you are in some other country near thailand and you are trying to get your affairs (marriage, home, etc.) in order, that you traveled to the near country to apply for the visa.

Bali is about $200 round trip. Bali has no US Embassy (it's in Jakarta) which makes a good excuse why you need to apply for a visa online at the Thai Embassy - USA.

The website is rigid but I have found the people processing the application are flexible and friendly, like Thai people usually are.

And this is exactly why getting your Non Immigrant visa before you arrive in Thailand makes life so much easier!

You should have got your Non imm O before you arrived. So much easier

Ask advise with thaivisacenter

In order to apply for a non-O marriage visa you must have the 400,000 in your account, meet all the paperwork requirements, and ALSO you must have at least 14-21 days left on your stay, depending on the immigration office. If you won't have that long left once you get all of your paperwork settled, then you'll need to leave and re-enter to get additional time.

Get a agent to do it all