Just go this website and u can search for the apartment up to your standard.
http://www.thai4rent.com/mambothai4rent/
By the way, if you are thinking of renting nasa vegas, please remember to ask for the new building because the old building sucks!
If you are talking abt accessiblity, I will recommend Duangporn Mansion located at Ratchada Soi 3 which I had previously stayed before it's the best location with Rama 9 mrt and Fortune Centre within walking distance plus the rent is 4500baht(new building) per month excluding electricity bills. The most important factor is you can surely get lotsa of kangtao staying there as Soi 4 is opposite there are plenty of action available.