<p>The generalized mode III fracture loading was conducted on edge notch disc bend sandstone specimens with three bedding configurations after thermal treatment at temperatures ranging from 75 to 600 °C. The influences and underlying mechanisms of thermal and bedding effects on mode III fracture behavior were analyzed based on acoustic emission (AE) localization and 3D scanning reconstruction techniques. The results demonstrate that the spatial relationship between bedding planes and the prefabricated notch significantly influences the strength and fracture characteristics. Specifically, specimens with short-transverse configuration exhibit lower peak loads (12.00% lower than divider configuration), reduced fracture energy (the initial fracture energy and peak fracture energy are 56.32% and 23.49% lower, respectively, than divider configuration), and lower stress intensity factors (the initial stress intensity factor and peak stress intensity factor are 22.82% and 13.37% lower, respectively, than divider configuration), making crack initiation more likely. Thermal effects also influence mode III fracture behavior, as both the stress intensity factors and fracture energy gradually decrease with increasing thermal treatment temperature. Furthermore, the high-temperature (400–600 °C) treatments tend to mitigate the influence of bedding configurations. The medium-amplitude (50–70 dB) and high-amplitude (70–90 dB) AE signals are critical indicators of mode III crack initiation and propagation. Temporally, these signals predominantly occur as sustained events during the crack propagation and macroscopic failure stages following crack initiation. Spatially, the medium-amplitude and high-amplitude signals are primarily concentrated near the prefabricated notch. In contrast, the low-amplitude (30–50 dB) signals caused by pore closure and grain friction are widely distributed throughout the entire duration and spatial extent of the tests.</p>