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.
I guess you're asking about the exit requirements? I don't think you need to concern about it. You can buy your Langkawi tickets before coming to Thailand. If for some reason that doesn't work for you, you can buy a throw away bus ticket from Hat Yai (Thailand) to Penang (Malaysia). I think you can also book a boat from Koh Lipe to Langkawi. Koh Lipe has an immigration office.
Depends on the immigration department. You may want to figure out the places you'll likely be at/around 2 weeks before your visa expires, then ask about that immigration office's policy/practice.
I have heard that people in Pattaya can extend 2 weeks prior and I have been told by the pattaya immigration office that I can only extend the day it expires (I have a feeling they were given me extra hassle because of my visa history).
I have no specific knowledge on the matter... But I have read in the news that Thailand pursues filming in the kingdom and the financial gain. Fast and Furious and some Lotus movies/shows were filmed here, those people don't look Thai (Asian), I suspect some how they were able to work legally.