I'm surprised there are no reports of success stories as of yet.
I did email the Hong Kong Thai Embassy asking if a US citizen staying in Hong Kong could apply for the DTV visa from the official Thai e-visa website. They said YES.
I've also emailed the South Korea Thai Embassy with the same question but I'm still waiting on a response. While I was in South Korea on the KETV visa earlier this year, I was able to apply and get approved for the Thailand TR visa through the Thai e-visa website. I'm hoping the DTV is the same.