In some recent on-board space plasma observations, it has been studied that high streaming ions play a major role in the physical mechanism for nonlinear wave structures. We have investigated here ion-acoustic solitons in a plasma with non-thermal electrons and weakly relativistic ions. Such plasmas occur in plasma sheath of boundary layer of earth's magnetosphere, Van-Allen belts. We have set up a KdV equation. This equation is solved in a stationary frame to obtain the expression for the soliton phase velocity, soliton width, peak soliton amplitude and soliton energy. These quantities are significantly influenced by relativistic effect, the non-thermal electron parameters and ratio of ion to electron temperatures. It is observed that for specific range of non-thermal parameter values, we obtain compressive solitons and above which the rarefactive solitons are observed. The problem is then extended to two dimensions and Kadomtsev-Petviashili equation is derived and its solution is characterized over a wide range of parameter regime for nonlinear wave structures.