I managed to achieve this function. Although the process is a bit convoluted. It does work.
Steps are
1. "when file is created or modified"
2. "Send a HTTP Request to SharePoint"
3. Parse JSON
4. Check Condition
5. is status == checked in, then do something, else terminate
HTTP URI is:
_api/web/getFileByServerRelativeUrl('/sites/TestFileShare/@{body('Get_file_properties')['{Path}']}@{body('Get_file_properties')['{FilenameWithExtension}']}')/checkOutType


