Forum Discussion
Office Online: Word and PowerPoint Documents open in Edit Mode
https://answers.microsoft.com/en-us/msoffice/forum/msoffice_sharepoint-mso_winother-mso_o365b/word-online-documents-opening-in-edit-mode/be77b404-96c7-4f7c-8420-9ab36f298c99?rtAction=1537886139257&tm=1537886178755
It doesn’t look like MS are going to change it…
The behaviour that files opened in Word Online is directly in the edit mode is a behaviour in SharePoint Online by default now.
As a workaround, you can set Require documents to be checked out before they can be edited to Yes in Version settings in Library Settings. Meanwhile, I suggest you submit your feedback on our https://sharepoint.uservoice.com/forums/329214-sites-and-collaboration/suggestions/34393561-requests-for-correction-on-behavior-to-open-in-edias it is the direct way for product developers to know users’ requirements.
I have followed the link and voted