Yes, your parents can report you missing. They cannot however
insist that you be returned to the country if you did file the
right form of papers and they were informed. You are afterall,
above 21. (As you claimed).
The general public can request to track you down too if you
contravene laws, abscon or have broken any contract and so on that
you have entered in.
Judgment can be obtained against you, whether you are in Singapore
or not.
And the courts can order a trace of your whereabouts to establish
whether you are alive, dead and so on after a couple of years and
list you dead and distribute your assets to your family
members.
You still have work permit, residency, credit issues to work out
even if you were to go off to China to work w/o informing your
parents.
And for that matter, China takes very dim view of fellas who does
not have the required visa, permissions and so on.
