Can I use a thumbprint instead of a signature for the Will?
If you (the Testator) are able to hold a pen to sign and has been using signature for recent documents, then it is very much preferable to hand sign all pages.
However should the Testator be unable to (e.g. illiterate or too weak to), then make sure the same thumbprint is to be used throughout.
Even for Lasting Power of Attorney forms in Singapore, thumbprints are allowed as well!