The feedback between tectonic events and surface processes fundamentally shapes landscapes and lithospheric deformation. However, the quantitative interaction remains poorly constrained. While numerical simulations offer powerful insights, 3D numerical models that couple thermo-mechanical processes with landscape processes remain uncommon due to the mismatches in temporal and spatial scales. Here, we present a 3D coupling methodology that integrates the thermo-mechanical code LaMEM with the landscape evolution code FastScape. A finite-difference marker-in-cell technique solves the thermo-mechanical processes, and a sticky air layer at the top boundary, combined with an internal mesh, effectively and stably simulates the free surface. Each timestep is synchronized with a finite-difference landscape evolution model. The timesteps of LaMEM are read by FastScape, which then subdivides them into smaller, iterative intervals to simulate surface processes. We demonstrate that the coupled model operates efficiently and stably. We validate our couple model by applying it to three classical tectonic regimes: oceanic subduction, continental collision, and continental extension. These cases converge quickly and align well with geologically realistic results. This approach provides a powerful, quantitative tool for exploring the bidirectional feedback mechanisms between the deep Earth and its surface, offering insights into the genesis of complex geological structures and landscapes.