I don't know of any I'm afraid as I'm working out here, there may be some on here already so take a look at the search function. Alternatively, this may be a case where Google is your friend.
the visa is legit as in it's legal but if you're not actually volunteering then you're in breach of your visa terms. There are foundations which you can volunteer for and get a visa through them, again not cheap but at least you don't run the risk of falling foul of immigration nor being held hostage by an agent.
If you're prepared to part with lots of money to get a volunteer visa and not volunteer then go ahead. Just be warned that if you want to change visa then you may need to cough up more money to the agent to help you.
There are a few people on here who have said they've gone down that route, I'm sure they'll share their experience if they read your post.
then yes you'll most likely be asked for a return flight by either the embassy and/or airline. Either buy a return flight or just get a cheap one way flight to wherever outside of Thailand within 45 days of arrival.
Presumably you're on a visa exempt for 45 days? In which case you can get one extension for 30 days.
After that you might be able to get an unable to travel due to covid extension but that will depend if they extend that or not, we won't know more on that for a month and a bit. If they extend it then that may take you through to Jan.
If they don't extend then it's going to come down to what exactly you're doing and what you plan on doing going forwards, as Stuart above says.