(Author's surname, Year)
This was seen in an Australian study (Couch, 2017).
OR
Couch (2017) suggests that…
Author, A. A. (Year). Title of thesis [Type of thesis, Name of institution awarding degree]. Name of archive or site. https://xxxxxx
Author, A. A. (Year). Title of thesis (Database Publication number, if assigned) [Type of thesis, Name of institution awarding degree]. Database Name.
Taffe, S. (2017). The Federal Council for the Advancement of Aborigines and Torres Strait Islanders: The politics of inter-racial coalition in Australia, 1958–1973. [Doctoral thesis, Monash University]. Bridges. https://doi.org/10.4225/03/59d4482289ea4
Bozeman, A. Jr. (2007). Age of onset as predictor of cognitive performance in children with seizure disorders (Publication No. 3259752) [Doctoral dissertation, The Chicago School of Professional Psychology]. ProQuest Dissertations and Theses Global.
Author, A. A. (Year). Title of thesis or dissertation [Unpublished Doctoral dissertation or Master's thesis]. Name of Institution.
Imber, A. (2003). Applicant reactions to graduate recruitment and selection [Unpublished Doctoral dissertation]. Monash University.
For further guidance, see the APA Style website- Published Dissertation or Thesis, Unpublished Dissertation or Theses.