Not sure you need to be physically in the US. I got mine all online from the Thai Consulate that was closest to my home address. Your air ticket probably needs to originate from the US.
Wow, Phuket will take a hand drawing but prefer a google printout due to the coordinates on it. When they inspected the hand drawings, the tech actually looked it up on the phone and then wrote down the coordinates for the residence.
Financial requirements is 800,000 Thai baht; that’s only about $23,000 US dollars. You can check on Thai immigrations website for forms and the requirements.
If your son is old enough to get married, he should be able to figure out the stuff by himself. Or at least ask for himself🤪. Even being married to a Thai only allows you to get a non-immigrant O visa, which is good for 90 days.