For a start the "object center
" property of the object should be set and placed lower on the screen compared to the character (lower, translates into closer to the camera) - if you wish to make it always stay on top of everything, you can put it as further down as possible (I think you are even allowed to have it below the scene image by a couple of pixels)
(see the first image)
the tricky part (that I didn't realize at first), is that you also have to set correctly the order of object inside the list of the scene objects (see the second image)! The simplest way (given that you have defined the object center already), is to press the the yellow up-down-arrows icon as seen on the second image!