What should I know about traveling to Thailand with a one-way ticket and applying for a volunteer visa?

I am leaving in 3 days for my 3rd trip to Thailand! Excited but nervous about a few last minute details...

1) Has anyone ever experienced any issues with a one-way ticket to Thailand? I have a one-way flight to Bangkok, and didn't buy a return flight because I am planning to stay for an undefined period of time (and didn't want to risk losing money on a flight change).

2) I am planning to volunteer with a nonprofit on the Burmese border once I arrive. They said that now you have to apply for the volunteer visa in person at a local embassy (apparently this just recently changed). So I assume I will apply for the 30 day tourist visa at the airport then apply for the 1 year volunteer visa once I arrive at the nonprofit center? Or do you have any other suggestions?

3) Can anyone tell me the cost of the application for the 1-year volunteer visa? I have found a couple of mixed answers (and it doesn't help matters if it was recently changed).

Thanks so much!!! ✨🙏💜