You can use Threema, Threema Work, and Threema OnPrem on the same device.
Please note, however, that a phone number or email address can only be linked to one Threema ID at a time (i.e., either to the Threema ID used in Threema Work or to the Threema ID used in the standard Threema app). Also, it’s not possible to use a Threema ID in both the Threema and the Threema Work app at the same time.
