hey sweets, I understand the parent who doesn;t approve of plastic surgery (:
What I would suggest for you to do is to just save up enough money and do it yourself. And technically I don't think you need your PARENT per se, will anybody above 21 do if say they are your legal guardian? I mean, you're Singaporean right? So I don't think he can trace if the person is REALLY your legal guardian.
In a worst case scenario, just do what we all did in secondary school and forge your dad's signature on the paper (:
OR!!! borrow ID. as in, when they ask you for identification, give them the borrowed one.
It really all boils down to HOW BADLY you want to do your face.
If you want it bad enough, an age limit requiring parental consent won't stop you
lemme know how it goes, good luck!