You will do the e-visa application on-line and then send them your passport by mail, with the approval if you have one or with the other documents requested, you will also include a return and stamped envelope for them to return it to you in. I used to do all of my Visa applications by mail which included the application and all of the paperwork as well as the paperwork and payment sent to them as I lived up near Redding, Ca. Please read the instructions on the Consulate General Los Angele's website carefully to understand what type of mail services they will accept. The individual I always received e-mails from when I had questions was Bernard, but that was when I was doing my Non-Imm O Visa applications and then my initial O-A Application. The last time I did it in person as I was flying through Los Angeles to Thailand, and decided to hang out in Hollywood for a few days, that was in 2019.
For the LTR Visa it says this
Ignore my comment about mailing in anything for the e-visa, this is a pop up when I just went to see the website and check the e-visa.
https://thaiconsulatela.thaiembassy.org/en/index