[Golden question]

So a lesson to all bros,no need apply duel citizenship for you Singapore born baby unless is really necessary cos legally now your baby can stay in Vietnam.
If your baby is red passport,the mother is consider breaking sg law by not returning the baby to sg and if she left sg without telling the other party for this case is the baby father,she is deem to break the law.Under international law,is consider human trafficking and is consider very serious.

End of the day,the innocent party is that baby,is hard to settle,fresh and blood.so u have to be calm like what some bro advise,think first on what u do,if your wife don't want cooperate for the well being or future for your baby,then is going to be tough for u.She is also the baby mother,at least she did not abandon her and throw at u and leave but whether is to hold u for 'ransom' for money in the future nobody know.Important is u must plan for your baby,always adults do wrong things,kids suffer