To make this leak proof, there should be 100% infill.More number of top/bottom layers.Print with a thick layer diameter.In case of ABS, acetone can be rubbed so that the material slightly melts and fills all the pores.Epoxy could be sprayed to seal off all the pores.Lid will be permanently glued to the body and then sealed with epoxy so that there is no water, gas leakage.