72 hours before ARRIVAL. Some people have stop-overs or layovers or have a longer journey. Thailand doesn’t care when you leave but they do care when you are going to arrive.
I was a notary for many years in the US. We did not authenticate documents. The notarization only meant that the signature on the document was signed in person and that said person presented legal identification.
Not sure if you’ve read all the requirements but she will need to be married to you for at least 10 years before she’s eligible. This holds true for American-to-American marriages.
it was worth the $30 to not be questioned by the airline. I had a bad experience once in Asia flying to US but with a 30-day “layover” in Europe. I was also told if I left that space blank that I could not get that TDAC. Could have been bad advice.
When I applied for the Thai Digital Arrival Card 3 days before I arrived, the website asked for my departure info. I had booked a ticket from Thailand to neighboring country for $30 US. Once I entered that info, I was ok. Someone else on this site said they wrote in that they were leaving Thailand on a bus and put in a date. You might try that instead.