Is your wife already in the US? I believe that's a basic requirement.
Last I knew the marriage visa was taking about a year, not years. It's also a much better experience for your spouse because they'll already have their full green card when they get to the US. That means they can start working and traveling immediately and it'll result in much less paperwork and cost a lot less too (by thousands of dollars).
Don't fly to Thailand then apply for a non-O visa. Apply for the non-O visa now from the Thai embassy, or you won't be able to open a bank account in Thailand.
In order to apply to convert to non-O visa in Thailand, you must already have a Thai bank account but you cannot open a bank account as a tourist. Therefore you need to get the visa before you travel.
Once you arrive you should be able to open a bank account with the non-O you get from the embassy. Then transfer the 800,000 baht to your bank account and you can apply for the 1-year extension after the money has been in your account for 2 full months.