Do You Need a Work Permit on a Volunteer Visa in Thailand?

yes, and so far the comments as 4x yes should be enough and how to get a work permit is not really Visa related.

Visit the Ministry of Labor in your area, get the hand out with requirements, fill in the application form, copy the asked documents, apply for the work permit, relax, pick up the work permit and start doing your volunteer work. Good luck.

Yes, you need a work permit with a Non-O visa to perform volunteer services. Your organization should give you those documents to submit to the local labor office.

Yes you need a work permit to volunteer,