What is the length of extension I can get for my Non O visa and can an agent handle the application for me?

The individual has a Non O multi-entry visa and inquired about the potential length of extension available after 90 days, as well as whether they need to apply in person or can use an agent. Responses advised that with the proper financial documentation, such as having 400,000 baht in a Thai bank, a one-year extension might be possible. They also mentioned the necessity of personal attendance at the immigration office, particularly in light of potential COVID-19 related extensions.