Pabili ng ube = Please buy ube/purple yam. It's a polite request already because the imperative command would be "Bumili/Bili ka ng ube" (Buy ube) or "Bilhan mo ako ng ube" (Buy me ube). But in most occasions, people use "pabili" in place of "pagbilhan" (sell someone something) which you'll often hear in stores. So if you say "Pabili ng ube" to a storekeeper, he'd take it as "Sell me ube/purple yam." Good luck! :)

[ Pabili ng (something)~ ] -> is a phrase used to express the "intention" of buying something from a "store" or from a "vendor". [ Pabili ng ube. - informal ] [ Pabili nga po ng ube. - formal ] -> they literally mean "Let me buy ube." or "I'd like to buy some ube, please." [ I want to buy ube. ] -> in English is "Gusto kong bumili ng ube." (^_^)/

yes.. :)

By the way, "ube" in English is "purple yam/winged yam/water yam". Scientific Name: Dioscorea alata. ^_^