What documents do I need to provide to extend my Non-O marriage visa based on monthly income in Thailand?

It is possible if your employer agrees to support you. You need a bunch of documents from your employer as well as your tax documents. You have to get the detailed requirements list from the local immigration office ASAP and talk with your employer immediately.

They may take time to prepare documents even if they agree to provide them, some have to be obtained from or certified by the government/official departments. Those include company registration, tax documents, etc.

If the current visa itself's validity ("valid until" or "must be used by" date on visa) is 9 December, you may want to consider bouncing for the last time on or before the date.