What documents can I use to verify residency for a Non-O Volunteer Visa application from South Korea if I'm only visiting?

The original poster, a US citizen, is seeking advice on which documents to submit to verify their residency while applying for a Non-O Volunteer Visa for Thailand from South Korea. They are currently only visiting family and do not reside in South Korea. Responses from the community suggest checking with the Thai Embassy for specific residency requirements, as some embassies may restrict visa applications to residents only. It's also noted that obtaining a volunteer visa for Thailand has become increasingly difficult.