<p>This study offers a detailed analysis of how the thickness influences the structural, optical, and electronic properties of thermally evaporated 4,9-dimethoxy-7-methylfuro[3,2-g] benzopyran-5-one (<b>KHE</b>) thin films for advanced optoelectronic uses. Films ranging from 250 to 400&#xa0;nm in thickness were examined using X-ray diffraction (XRD), spectroscopic ellipsometry, Fourier-transform infrared (FTIR) spectroscopy, and density functional theory (DFT) calculations. XRD verified the monoclinic crystal structure and showed that increasing thickness increased crystallite size (from approximately 93 to 97&#xa0;nm) and decreased dislocation density. Optically, thicker films had a stronger dielectric response, with the real part (ε₁) over 40 and the high-frequency dielectric constant (ε_∞) reaching 4.104. The direct band gap decreased from 2.90 to 2.43&#xa0;eV, due to improved π-electron delocalization. Thickness also significantly improved nonlinear optical parameters, boosting the third-order susceptibility (<i>χ </i>^<i>(3)</i>) and two-photon absorption coefficient (<i>βc</i>). This study explores the optical limiting behavior of <b>KHE</b> thin films under laser irradiation at 635&#xa0;nm and 530&#xa0;nm, revealing a pronounced thickness-dependent nonlinear optical response. The results show that the limiting efficiency, reflected by a substantial decrease in normalized transmittance, varies with film thickness, with the strongest performance observed under green wavelength excitation due to enhanced reverse saturable absorption. These findings demonstrate that film thickness serves as an effective parameter for tuning both the optoelectronic and nonlinear optical characteristics of <b>KHE</b>, establishing it as a promising material for integrated photonic systems and laser protection applications.</p> Graphical abstract <p></p>