It would be a really giant tomb bigger than those of Chinese Emperors. I would make it full of labyrinth, non-harmful traps, puzzles, hidden items that need to be collected all throughout the world and tons of other stuff needed to reach the room with my coffin. I would liquidate all my assets and convert into gold, make this gold surround my coffin. To lessen security leaks the process of building tomb would be distributed between several workers and companies so that all would know only a small part of the plan and also make them sign nda. I would create a testementary trust fund which would manage the security of the tomb to prevent cheating.