I have noticed that most foreigners (west and east and everywhere) often mistook "kumusta" as single greeting phrase like "Sawasdee" in Pasa-Thai or "Menggalaba" in Myenmar.
"Kumusta ka" or simply "Kumusta" actually means 'How are you' in Filipino. It derives from the Spanish phrase "Como estas", however, like I mentioned above, they mistook it as a greeting since Filipinos tend to say 'how are you' first when they meet someone they knew.
(my friends sometimes got confused when i replied to them... ^ ^" )