Hi, i meant submit paper before submission of thesis. For example, different chapters in your thesis may cover some different aspect, so while working on chapter 4 scope for example, results covered by chapter 3 could be sent for the review process. Even when your paper is published, it will be under your name but true, someone could potentially make a bigger breakthrough. Personally, I think the best way is to time so that the status is accepted but not published yet although some journals are very efficient in uploading the manuscript before proof correction too.

However, you may also refer to several posts above about self plagiarism which is on another perspective. Some institutions have publication requirements, while some supervisors will insist on publication too, so you need to check this with your university/supervisor.