no it is not a small chance is a very good chance. If you present all the documents in a professional format and submit the application. K-1 visa is very often approved more so than not. The interview at the Embassy is the key to the approval process. 
normally if they send anything back to USCIS, USCIS will contact the applicant and request an RFE, which is a request for further evidence unless they are planning to flat out deny the application, but you are correct that could take a while 
take your documents to someone that has a scanner have them scan and save the files to their desktop and then use that same person to fill out the application once the documents are scanned and saved on your computer. It’s just a matter of selecting them and attaching them to the application. It’s very simple.m
you open the account in Thailand but once you come back to the United States, you can send money to your account in Thailand through the New York branch of Bangkok Bank. It is not a retail branch where they have walk-up service and things like that. It’s a commercial bank, but all you have to do is call them and get their routing number, you send them the money and they will forward it to your account and Thailand. When I called the New York branch to get the routing number and the instructions for sending money to my account in Thailand they were very helpful so make sure you do that.
I normally send money to my account with Bangkok Bank to the New York branch of Bangkok Bank. That way your transfer is less than the international fee is. Of course that is, if you are from the US.