That would definitely make sense with Monsters of Myth's recent confirmation that the Okaiyo Ocean is more inhabited (on the surface) than previously implied. Though, I'm not sure anything marks the Karyus Islanders as (necessarily) inspired by one of the various Pacific cultures other than the island location--the closest equivalent to their practice of guiding ghosts with lanterns that I can find is a Japanese festival.
I think we can definitely assume they're not from Avistan, northern Garund, Vudra, Tian Xia, Sarusan, or anywhere landlocked though, and probably not Azlant, Kelesh, the Embaral, or the polar oceans/seas (given Geb contrasts them with a people from the "frozen north"). So Okaiyo Ocean would fit, but so could southern Garund, eastern Casmaron, the Obari Ocean, or somewhere off the coast of Arcadia.