International standards relating to a professor publishing a student's thesis work without the student as co-author
There is no international standard because authorship practices vary.  

COPE is the closest thing to a standards organization, but they do not publish authorship standards, or any other kind of standard.  

References:

https://publicationethics.org/files/Recognise_Potential_Authorship_Problems.pdf

https://publicationethics.org/files/u7141/best_practice_for_issues_around_theses_publishing%20(1).pdf

Academia varies more than you think it does – The Movie (why there are no standards)

Publishing a student's thesis without their name is certainly unethical.