Applying S1 visa for my son with Malaysian passport

I am a Filipino single mom, my ex-husband is Malaysian and my son is registered in Malaysia and using Malaysian passport. I'm working now in China for a year and my son was taking care of my mom in Philippines. He's not registered yet in Philippines, his passport and birth certificate are registered in Malaysia. Do we really need for him to register in Philippines so I can apply for him an S1 type?