If my oldest son was told he can marry a woman in the Philippines and bring her to the US and marry her again, can he do this?

Significantly more information is needed in order to provide a legal analysis about your son's ability to sponsor a wife and about the appropriate way for her be able to come to the U.S., and errors can have very harsh immigration-related consequences. There really is no substitute for your son and his fiance or wife to consult with an immigration attorney who, after learning all of the relevant information, could advise about eligibilities, options and strategies to attain the couple's immigration-related goals, and who then could offer legal representation in the often complex application process.