Agree. I am amazed that anybody would consider $100 a night in Bangkok "inexpensive." Remember you must judge on an absolute basis, by local standards, not by some benchmark based on your home country.

I think Thailand is good for an initial foray into SE Asia--good infrastructure, easy to travel, easy to meet people. But I wouldn't suggest spending your entire month there. I would say that limiting this trip to some of the surrounding mainland countries of SE Asia makes the most logistical and financial sense rather than heading overwater to Indonesia or the Philippines--save those for the future. In addition to Thailand, you should consider Cambodia and perhaps Laos. I'm not as averse to sending a first-timer to Vietnam, but I think given time constraints and the fact that a good Vietnam sampler trip really takes 2-3 weeks at least, I'd put that off unless your research puts in high on your priority list. All of these countries work well for a solo traveler on a budget. You don't need to take group tours for anything unless you want to (or to split costs)--and most activities can be arranged in real time as you go. In the other direction, peninsular Malaysia is OK but more developed and more expensive. My personal favorite, Myanmar, is probably better suited to a more experienced independent traveler and it won't have the fellow traveler-meeting possibilities or nightlife that you might be looking for.

Remember that in August, Andaman-side beaches of Thailand such as Phuket, Lanta, Khao Lak will be subject to monsoonal rain patterns, and water will generally be too rough for swimming and uncomfortable for boating. Services to outlying islands may be curtailed. If part of this trip will be beach-oriented--consider the Gulf of Thailand side instead. Skip Pattaya area entirely.