A computational fluid dynamics based simulation for the motion of a ping-pong ball under buoyancy of water is presented in this paper. We utilize the cumulant lattice Boltzmann method (LBM) and a multi-direct forcing immersed boundary method for the coupled computation. Virtual mass approach is applied to stabilize the solution of Newton's equation when the solid-to-fluid density ratio is very small. In order to enable the code for large-scale efficient simulation, the graphics processing unit (GPU) is used. Our simulation is accomplished with 12 Tesla P100 GPUs. Finally, the wake structure and path instability of the ping-pong ball are shown in the reuslts.