@natebowling I recently spent some months in Bangkok, and while I didn't have a private rental, I can recommend the Wire Bangkok hotel/guesthouse in Phra Khanong neighborhood.

It's modest and modern, the staff are kind, the price is okay and they do weekly/monthly rentals. I paid weekly and stayed there 4 months. The wifi is good (I worked from my room near daily) and there is also a working lounge that is often empty. The managers also run a quiet cafe by the first floor reception.

It's only about a 5 minute walk from Phra Khanong BTS station, but the layout of the working-class neighborhood keeps the area quiet. So, not in the expensive downtown part of Bangkok, but pretty handy to it. Plenty of cafes, a laundromat, and like three 7-elevens within a quick walk.

It might be a good fit, or at least a place to land while you check out other neighborhoods and ask around locally for leads.