Yes. If you are receiving Medicare benefits, you can withdraw from your remaining HSA balance to pay for healthcare expenses and pay for your Medicare premiums (does not apply to Medigap or Medicare Advantage premiums).
However, you will not be able to continue contributions to your account once you are enrolled in Medicare. This includes pre-65 disability Medicare.
When you are no longer enrolled in the CDHP, you will become responsible for paying any administrative bank fees previously covered by the state.