Not going to happen unless she's from a wealthy Thai family and has business ties to Thailand and significant assets in her name. Unless you can buy her a Trump Gold Card. You might get a fiancee visa but it will take months and you so need to marry her within 6 months of her arrival.
you could investigate a remote customer service job with a USA company (phone support). But that job certainly isn't going to give you additional peace of mind.
No cases yet. But it is fraudulent. Whether it's prosecuted or not may depend on which way the wind is blowing. Not a risk l'd like to take with my life choices. Also, very true about the difficulty in break up.
Why do you want to use an agent for the finances? It contributes to the corruption and it's technically illegal and could put you visa at risk. It will also be harder to break away and do on your own in the future. If you have the means, do it yourself.