The fabrication of thick origami structures often faces two challenges. Thick origami is usually rigid and not flat foldable. This work demonstrates a technique for creating non-rigid, fully flat foldable, and thick origami. By harnessing the material properties of 3D-printed Polylactic Acid (PLA), thick origami panels that selectively exhibit non-rigid behaviors can be fabricated using living hinges. Constraining the deformation of these living hinges within the elastic regime of the material, robust flat foldable thick origami structures can be created. These methods are demonstrated in a parametric model of a thick origami flat foldable Kresling pattern. The kinematics and bistable mechanical properties of these Kresling structures will be characterized to demonstrate the viability and scalability of this technique.