Get on a class 2 train ride from BKK to Kanchanaburi. It's uncomfortable and hot, but it will give you a real Thai feeling and you'll arrive in a historically important city that has a ton of charm and lots of nature to explore. Get a bungalow right on the riverside. You can get on a boat that takes you upstream and then you can float down the river all the way back to your bungalow.
yes, that's what it costs when you're actually volonteering. If you just buy one, you're basically bribing agents and immigration officers to get the visa.
Just check in at a normal hotel, tell them to register you on the immigration website asap, because you have to go to immigration. And then go get your address note and extension.
yes, you're on a tourist visa. This new Rule applies to Non-Immigrant visas.
But make sure to follow the news as things can change drastically and rapidly around here, which could mean you need to find another solution in March.