Can I apply for Kaiser insurance if I am no longer a employee but is willing to pay out of my pocket ?

Of course. You can buy Kaiser insurance like everyone else. Call the Membership number 800-464-4000 and see what plans they have for an individual.

You can apply for anything you want. Being accepted is another thing.

Yes, they also sell individual plans.

They would be happy to have you. Enrollment is now through some time in January. It's their open enrollment period when they streamline the process.

If your employer has 20 or more employees and you left your job within 60 days, you are required to be offered the option to continue your coverage.

- some states have this requirement when there are under 20 employees.

Otherwise, you can purchase Kaiser (if you are still in their coverage area) but the plan and the cost will be very different.

Yes.  And in my area, you can also apply for Kaiser on the ACA exchange, coveredca.com in my case.  If your income is low, the premium could be subsidized.  In 2018, our Kaiser was virtually free, as far as premiums.  Actually lower than it was when I was working.  But high deductibles.