hi Rose, the word "serve" can have lots of definition in tagalog and likewise, "serve it right" may be an idiom. do you have the complete english sentence (if there is) where you found this phrase? as an idiom, it may mean "ibigay ang nararapat para dito." :)

gawin niyong maayos, or more formally - ipaglingkod ninyong maayos...

This is where my knowledge of the Malay language actually comes in handy. x) Padan muka / Serves you right in Filipino is "Buti nga sayo" :)