Recently, process monitoring emerges as a breakthrough technology in industrial laser machines applications to enhance process stability and economic efficiency while ensuring high-quality processing parts and significantly reducing scrap rate. Furthermore, the latest advances in monitoring systems open a broad range of new opportunities to increase the capabilities of laser surface structuring. In this study, stainless steel and aluminum substrates are structured with a line-like geometry by Direct Laser Interference Patterning. A high-speed infrared camera is used to detect the thermal effects throughout the laser process. Simultaneously, a diffraction measurement system is implemented to analyze the quality of the fabricated periodic patterns by comparing the diffraction order characteristics. This specific combination of the systems allows a remarkably high-performance process monitoring and quality assurance. The obtained results reveal a correlation between the signals detected by the infrared camera and the intensity of the diffraction orders recorded with the quality of the surface reached.