I think they're refereed to as "Developing Country" or "Developing Economy". I think "third world" are more about peoples that are in a bad situation getting worse... Somalia for example (Or the US if you pay attention to US politics).
August was a couple of weeks ago.. I think you may have missed your plane.
If you asking the internet/facebook about weather a year from now... You deserve the answer you get.
I live near/on the Sea, in Pattaya. It rained maybe 3 or 4 times during the whole month of August (I have no idea what it will do next year). However, it's rained considerably more near by, and there have been very few sunny days.
You can play it safe and buy a cheap bus ticket from anywhere in Thailand to anywhere not Thailand. The cheapest I have found is Hat Yai to Penang. The cost 5 years ago was $12
I always put a date of 59 days or less.. I don't know that it matters. One thing to note is, if you need to show proof of onward travel. In the past, I have used bus tickets and just don't get on the bus.