In the APA 6th Ed. manual a doctoral thesis is called a dissertation and a master's thesis called a thesis. This reflects the academic nomenclature in the USA. In Australia, these terms are used interchangeably with thesis being the most common term. Theses is the plural form of thesis.
According to Anstee (2019) ...
...as it has been identified (Anstee, 2019) ...
Author, A. A. (2003). Title of doctoral thesis (Doctoral thesis). Name of Institution, Location. Retrieved from URL
Anstee, A. G. (2019). Independent school principals' wellbeing: Exploration of inhibitors and enablers (PhD thesis). University of Technology, Sydney. Retrieved from https://opus.lib.uts.edu.au/handle/10453/132830