Yes. A thesis and the subsequent published monograph are rarely identical. Monographs are often based on a thesis but are usually re-written to include new information such as comments from examiners and reviewers and to incorporate new information.
We recommend that you check the policy of your intended publisher, and discuss your publication options with your Research Supervisor.
Please note: you have the option to restrict your thesis to local access if you find your publisher insists on exclusive publication.