Can I convert my non-B visa to an O-A visa in Thailand or do I need to apply from another country?

The user is currently on a non-B visa and is inquiring about the possibility of converting to an O-A visa while remaining in Thailand, specifically in Bangkok. They are seeking clarification on whether this conversion can be done within Thailand or if they need to leave the country to apply for the new visa. Additionally, they are asking for the necessary paperwork required for the application, apart from income verification.