Monthly rent ranges from 9,000 to 15,000 baht per month for all the modern amenities. Wendy Guest House and A-1 Guest House are popular places in Siam Square, and cost 9,000 and 10,000 baht respectively. There are a lot of guesthouses in Banglamphu with basic accommodations for those on a budget. Basic rooms will have a ceiling fan, and may have basic furniture such as a nightstand or dresser drawer. Shared bathrooms will be in the hallway.
Guesthouses also have their own kitchen with Western and Thai dishes.
Those who prefer a less sterile atmosphere can rent old Thai houses in the Sukhumvit area, where a lot of expats live. You might have to find a connection in the expat community to live here, since houses are shared with two or three people, and modern apartments are for one or two people at the most. These antique-style houses are quite pleasant, with teak floors and traditional decor. However, they may not have air-conditioning, hot water, or Western bathrooms, unless they have been converted. Rent can be quite high, especially if you have maid service, which a lot of people who live in these houses do.