Can a 60-day or 90-day visa be converted to a year-long visa in Thailand?

A 90-day Non-Immigrant (O) visa can be converted to a one-year extension of stay in Thailand if you meet the necessary requirements. While it's possible to convert a tourist visa to a Non-O 90-day visa and then extend it for another year, you cannot apply for a Non-Immigrant OA visa within Thailand; it must be obtained from your home country or country of legal residence.