Repasting voids warranty, though ASUS might be willing to do it for you, considering that your computer is still under warranty.

Does replacing thermal paste void warranty ASUS laptop?

replacing parts, modifying parts, or even opening up the device to view the inside will usually void any warranty.

Does Repasting void warranty?

Not voiding your warranty when repasting also requires not getting in over your head when it comes to disassembly and reassembly. If you're not certain you can put it back together again (don't lie, the instructions tell you just how much disassembly is involved) don't take it apart.