Can I change my Non-O visa to a Non-B visa in Thailand?

You can change a Non-O visa to a Non-B visa if you have 15 days or more left on your current Non-O extension, but it depends on your employer's ability to provide necessary documentation. Alternatively, you may be required to cancel your Non-O extension and apply for a 90-day Non-B at a Thai consulate abroad. If your Non-O visa is based on marriage to a Thai national, you may not need to change it to apply for a work permit, but if it's for retirement, you will need to change it, subject to immigration office policies.