The primary way in which status as a theme is developed in this excellent tragedy is the way in which Lear willingly gives away his status to his two daughters who are unworthy, and thus delivers his kingdom into chaos and uncertainty. The loss of his status as King and father gives the opportunity for the less deserving to seize upon this vacuum and use and abuse his former power for their own selfish ends, thus resulting in chaos and cruelty for Lear's former kingdom. Thus your thesis statement could explore this process in more detail, and how the loss of status of Lear is linked to the fortunes of his kingdom. Basically, Lear's desire to keep the trappings of power without the responsibilities is what triggers off this tragedy, so a thesis statement you could use might be:
Lear's choice to pass on the responsibilities of his kingdom to others lowers his status and leads to the chaos that descends upon his kingdom.
This thesis statement will give you a chance to explore these issues in more detail.