Bangladesh, hands down. I stayed at a hotel that was well known but spartan in a room with an en suite shower and sit down toilet for under $2 per night for a double (Hotel Al Razzaque in Old Dhaka). Most full meals at restaurants in the city will cost you about Tk50 (about $0.75) per person, but if you go to upscale Gulshan or Banani you can get really nice menus for $4.50-$6.00 per person. Rickshaws/auto rickshaws are so ridiculously cheap as to be not worth adding up, even if you end up paying triple the going rate as a foreigner.

Unless you plan a lot of shopping or going to private clubs and staying at posh hotels like the Shonargaon or the Sheraton in Dhaka, you'd be hard pressed to spend more than $20 a day. Even when we sprung for a really nice place on UN road for the last night of our trip, I think it cost us $25 for the night.

Admissions to the museums and tourist sights that there are are ridiculously cheap (I'm talking like a couple US cents here).

Lovely country with lovely people and just crazy cheap to travel in.

peace,
~Ben~