What are the requirements and processes for obtaining a Thai volunteer visa?

Questions about Thai volunteer visas:

- does the organization typically cover the costs of the visa?

-if not, how much do they generally charge the volunteers?

-what is the hour requirement to qualify for the visa? Or is it just proof of accomplishments not tied to hours?

-is it generally the task of the organization or the volunteer to compile proof for the 90 day check ins?

-does the organization have to be officially registered as a place accepting volunteers/providing volunteer visas? Or can you volunteer anywhere (relatively speaking) and just fill out the necessary paperwork? In other words: What type of organizations can you obtain a volunteer visa by volunteering for them?

Thanks!!!