My door jamb is around 140mm, does the door have to be hung on the edge of the jamb like all the other doors in the house, or can i hang it toward the center of the jamb by 70mm so it can clear a wash basin when opened.
You can do so. It will complicate the strike plate mounting, perhaps necessitating a relief arc in the latch jamb. The centered door will only open (at most) 90 degrees before being stopped by the jamb.
Other options may be to reverse hinge side and latch or making the door out swinging.
You can as Daryl mentioned but I would strongly recommend only doing so if you have a way to positively stop the door from opening before it hits the jamb when open; there would be a hige amount of torque there and your hinges would certainly break the jamb itself in a short amount of time!