I do not think they have a quota. As per a link I shared above in a separate comment, the approval ratio for Thais for 2020 (as per Dept of State own statistics) is 75%.
Since mid last year I've been helping Thai people find interview dates and just generally being immersed in the whole US visa space (but NOT a visa agency, ...yet) there's a lot of stuff people do wrong.
But lots of weird going on, literally offering a job such as a restaurant job IS a red flag for overstaying a B2 'tourist' visa. Your wife would've needed to apply first through a marriage visa, go through the process of getting a green card, and only then would she be allowed to work.
Employment visas are WAY more complex and lengthy and require for the company to show they've tried to find help in country first.
7kg carry on (but they didn't really check mine), and 20kg it's extra for 500thb. I ended up shipping it via Kerry Express to my address in BKK, for about 400thb (it was actually 75kg worth in 3 bags, easier to just have it delivered at my door vs me carrying in the taxi).
You can just go to AirAsia's website and go through the booking process, you'll be able to see the prices of checked luggage options (20,25,30kg etc).