What documents should I provide as proof of accommodation for my Thailand DTV visa application?

I went through this embassy before the price rises for a METV, and during the covid STV era. I ended up reaching out to a couple of condo owners on AirBnb in the area I wanted to stay asking if they would consider a long term lease and I explained my situation of requiring 9 months and needing it for the visa. The owner helped me out with preparing a 9 month lease agreement and provided a copy of their national id card. This was after I booked an initial 60 day Airbnb booking with them to secure their trust. I have stayed at the same condo each year I return back here.

What entry scheme are you using, soft power or digital nomad? This is a bit of an unreasonable request, you could send your one month booking along with the cover letter stating that you're looking for more long term accommodation once you get there. You could also say that you only plan to stay for a month on your initial visit. That embassies prices are ridiculous and it seems their requests are too.