Create an action :
Your pics aren't square but you want your thumb to be, so here's how I would do it.
Resize the image to 120x160 or whatever it ends up being with the aspect ratio.
Set the mask tool at fixed size (88x88 - 100x100) and one click on the image gives you the thumb size you want.
Add a step to sharpen, adjust contrast etc.
I know it's not the easiest way but it's my way
