What should I do to extend my Non-B visa if I cannot return to my country because of flight closures?

They will stamp extension till Nov 30.

Asking for extension of stay based on necessity is not an extension of your Non-B visa. It merely gives you some time before you eventually return back to your country. To do so, you need to make a case explaining the reason why you can not go back to your country and provide any evidence to support that reason. If you can not provide evidence and your embassy won’t issue a note to support your extension, you might have to consider other options such as

1. Return to your country

2. Extend your non-B visa by proper means, such as getting a job, getting your business partner to support reason for your extension, investing in a business in Thailand, etc.

As every local immigration office seems to interpret the rules slightly differently, your best bet is to call into your local office and ask them.