Understanding the details of laser-plasma interaction in sub-micron films at moderate intensities is essential for accurate description of the early stage of laser interaction with low-density foam targets, which hold promising potential in research and applications, related to the inertial confinement fusion, equation of state studies, high-energy particles and radiation sources. This work presents the results of numerical study of laser interaction with sub-micron films at intensity level of $\sim {10}^{14}$~W/cm${}^2$, utilizing a kinetic framework via a Particle-In-Cell~(PIC) code. The results of PIC modeling were cross-compared with those obtained with a hydrodynamic code. The presented analysis unraveled the role of the nonlocal and electrostatic effects in the processes of laser heating of ultra-thin films and their expansion; based on the obtained results, limitations and recommendations for use of hydrodynamic codes for modeling of more complex targets like foams were formulated.