You don't want a "marriage visa" unless you intend to live permanently in the US. It's not for temporary visits, takes a year or two (or maybe more now, who knows), and costs a few thousand dollars.
It can be difficult for a Thai married to an American to get a tourist visa. They will assume your plan is to live in the US permanently, and you are just trying to avoid the long expensive process of getting a marriage visa. To have a chance at getting a tourist visa she will need to show strong ties to Thailand and have a strong reason to return. If she has a job, owns property, has kids or aging parents in Thailand that she needs to return to, she will have a chance to get a tourist visa.
The process is outlined on the US embassy website. There is nothing any visa service can do for you except hold your hand while you complete the process.