can car license be converted to motorbike license?

No you need a Singapore motorbike license.

You can only convert you car license for a car license.

cheeha thanks for the clarification, I missed the fact he only had a car license....

I had my Texas auto licence about 90% converted to motobike licence. I only had to pass driving test.
I got both my Vietnamese car and motobike licence for about 100used. I just gave my wife's friend a copy of my passport and my Texas drivers licence and he set up everything, he even got me to the front of the line to take motobike driving test which was nice as it was very crowded that day.

Yes , you'll need to take motorbike driving test and no need  writting test if you have had singapore car license . Then after 10days you will getting the Vietnamese motorbike license .

oh... thanks . gee , where to take the test and all these??

Dear VungTauDon,

Could you please so kind as to introduce me your friend so that I can tell my Japanese friend to take a driving test to get a motorbike license

Thanks!

I will ask my wife but we are not in HCMC we are in Vung Tau