Does AT&T works here in the philippines? Only at&t is applicable for iPad

I don't believe AT&T is a cell carrier in the Phillipines. But if what you are saying is you have an AT&T version iPad, all you need to do is get a Micro-Sim card from a carrier in the Phillipines as that model iPad operates on GSM, which is predominant throughout the world.

Are they locked like I phones that need to be unlocked before u can use with another carrier?