There are more "guest friendly" hotels that are in the 1500 baht range and below than not! Even a hotel that charges 600 baht per night will have hot water, private toilet, cable TV and maid service.

Another example:
Fortuna Hotel, Sukhumvit Soi 5, near the Foodland Supermarket (good restaurant open 24 hours.) Decent "all you can eat breakfast buffet" open to the public for around 130 or 140 baht but free to hotel customers. Short walk to Nana Skytrain stop, close to malls, street vendors, bars and travel agencies for tours and plane tickets.
http://www.fortunabangkok.com/