In order to search for a thesis topic, you may want to do the following: search on Google Scholar, and write the words, say "Sustainable Insurance". You will get many papers talking about such topic. Try to skim through these papers (especially their Abstracts) for 2 main reasons: 1- to see what has already been written about the topic, and 2- to check for the research gap/gaps that you want to cover in your study. This is a start. By the way, you may want to keep such relevant research papers to use them as references in your thesis. You may use the latest papers published about the topic.
Sustainable insurance systems usually have a state-based and a private-sector pillar, in which different financing principles are pursued (pay-as-you-go = paygo or funding). In order to achieve stable and sustainable social security, both systems must be efficiently coordinated. For details see:
(1)
(PDF) Insurance Theory, Social Security and the Financial Markets Crisis. Available from: https://www.researchgate.net/publication/320471815_Insurance_Theory_Social_Security_and_the_Financial_Markets_Crisis [accessed Mar 07 2022].
(2)
(PDF) Insurance Theory and Social Security. Available from: https://www.researchgate.net/publication/281651015_Insurance_Theory_and_Social_Security [accessed Mar 07 2022].
(3)
(PDF) International experience with alternative forms of social protection: Lessons for the reform process in Russia. Available from: https://www.researchgate.net/publication/46115984_International_experience_with_alternative_forms_of_social_protection_Lessons_for_the_reform_process_in_Russia [accessed Mar 07 2022].