Can an application for a visa extension be denied in Thailand after long-term stay?

The question addresses the possibility of having a visa extension application denied by Thai immigration for someone who has been living in the country for an extended period (5+ years) with multiple METV entries. Responses from the community suggest that while it is rare for such extensions to be denied, the decision ultimately lies with the immigration officer. Some users noted that denials can occur, particularly for tourist visas, and mentioned options like filing an appeal.