  We have studied the low-lying electronic structure of a new
ThCr$_2$Si$_2$-type superconductor KNi$_2$Se$_2$ with angle-resolved
photoemission spectroscopy. Three bands intersect the Fermi level, forming
complicated Fermi surface topology, which is sharply different from its
isostructural superconductor K$_x$Fe$_{2-y}$Se$_2$. The Fermi surface shows
weak variation along the $k_z$ direction, indicating its quasi-two-dimensional
nature. Further comparison with the density functional theory calculations
demonstrates that there exist relatively weak correlations and substantial
hybridization of the Ni 3$d$ and the Se 4$p$ orbitals in the low-lying
electronic structure. Our results indicate that the large density of states at
the Fermi energy leads to the reported mass enhancement based on the specific
heat measurements. Moreover, no anomaly is observed in the spectra when
entering the fluctuating charge density wave state reported earlier.
