Hi Dirra.
There are literally 1,000's of places to stay in greater Bkk for under 10,000 THB/Mo. in fact if you're just after a cheap and cheerful studio which is clean and tidy with TV, Internet, mini mart, salon, laundry service and so on, you'll have plenty of choices at around 6,000 THB/Mo.
I've not lived in Bkk studios for a good number of years, but there really are some resaonble places to stay within a few minutes walk from the Sky train and MRTA (underground) routes. I'm sure there are folks in here who are currently living in and can recommend such places to you so that you can build a short list before you arrive.
Failing that, probably one of the best websites for budget accommodation is
Easy Horpak
Good luck.
Aitch