You need your marriage certificate by your state and then certificate by the US State Department. Then certificate by Thailand and translated. Then you can register your marriage at the ambulate in Thailand.
My wife is thai and we got married in the US and we have done this with our marriage license. When we go back to Thailand we will get official translation done so we can register our marriage in Thailand.
We did this with several copies of the marriage license because I was told she may need them for changing her ID card, drivers license, Pass Port house papers, and name change.
Bangkok Bank asked the same thing. Just get a certificate copy of your passport at the Embassy. They put it in your file when you open your account. It's not a big deal.
You don't go through customs leaving the US and there is no requirement about how much money you take out. If you bring $10,000.00 or more back into the US you must declare it when you enter the US.
No I did not for the first part of the K-1 but I used a agent for the US Embassy part to arrange for background check, medical examination and helped with interview questions for her. They also arranged for the interview appointment.