If you ever wondered why the flag of Singapore, Indonesia, Umno and PAS circa-1950 shared the same red and white motif, it is likely because they adopted an ancient flag which represented 'Nusantara' - the Malay archipelago.
According to social activist Hishamuddin Rais, who has written extensively about the subject over the past decade, the red and white motif was dubbed the Sang Saka, which incidentally was what Umno called its flag.