The following are all potentially valid names for that body of water. South China Sea, West Philippine Sea, North Natuna Sea. There are more if you start to go

The following are all potentially valid names for that body of water. South China Sea, West Philippine Sea, North Natuna Sea. There are more if you start to go outside of English such as "East sea" in Vietnamese. Proposals for new names include Indochina Sea and Asean Sea. South Sea might be viable. It'd be nice to see the name settle as "The sea that can not be named".