She needs to prove that she will return to Thailand. Not just family, but a business that she owns and the finances required to sustain herself and return back to Thailand. Put a significant amount of money in her bank account every month, even if you withdraw it. It is true that a fiancee visa is easier to get and $600 is not a lot for that. Most attorneys want $1,000. These are lawyers and they normally won't lift a finger for less than a few hundred dollars. A fiancee visa takes 6 months or longer and you need to supply pictures of the both of you together and the ability to finance her trip. It usually takes 6 months or longer but sometimes you can get it done in 3 to 4 months. Again, money talks.

$50,000 USD

Yes, exchange to U.S. dollars in the Philippines or you will lose significantly when buying baht.

Get a dog and stay where you are until your financial situation improves, or you will be homeless in a strange land!