You definitely need to favor the cheaper countries and decide where your level of tolerance is. When I was 33 I took a buyout from a job and applied the 75% of an annual salary to a plan to travel the world for a year (the gap year I never had). Was very concerned about finances working out, even though I was using miles for the flights. I had a target of $60/day for everything outside those flights.

To do it I concentrated on SE Asia in 3-month chunks and tried for $10-20 on lodgings. Could have gone lower but if you watch the first part of "The Beach" you see one of the dumps you might get in the sub-$5 range.

All the SE Asian countries except Singapore and Brunei are likely to have something low enough, though you might be looking at a fan (it can get humid!) and shared bath. Overbuilt markets like Pattaya and Bangkok might even have options with air-con and TVs in the $10s. The indochina countries can be cheap but are also poor, and you can find a big bump up in comfort at $15 or $20 vs. $5.

On food there's street food but not everyone adapts quickly. There's usually no English signage or English spoken, but tourist-oriented places cost more.