Interesting topic, just looked into this now, because maybe airbnb, serviced appt or hotel for "longstay" might be one of my options.
When I read the price above, 45.000 baht..it might be worth to consider Majestic Grande in Soi 2. The name is changed into Hilton.
I stayed there a couple of times, and one time I stayed a full month for 60.000 baht. This was including breakfast and ofcourse all the standards you usually get in hotels.