This paper proposes a pulse-echo ultrasonic propagation imaging (PE-UPI) system capable of scanning an area of customizable shape for non-destructive evaluation of structural defects. The system inspects by detection of bulk waves that travel through the thickness of the specimen. This is achieved by joining of two laser beams, one each for the ultrasonic wave generation and sensing. A Q-switched laser is used for generating the aforementioned ultrasonic waves and a laser Doppler vibrometer (LDV) is used for sensing. The system also consists of a dual-axis automated translation stage for raster scanning of the specimen and a digitizer to record the signals. User can delimit the scan area in any abstract shape according to region of interest on the specimen. A graphical user interface (GUI) software controls all the individual blocks of the system. This software also manages scan area customization, signal acquisition, processing and display. The GUI is created in C++ using QT framework. Multi-threading is used for real time update of scan result while the scan is still on-going. This is achieved by realtime and concurrent acquisition, processing, and display of ultrasonic signals from the latest scan point in a scan area.