Can I use a any T-mobile Sidekick in Singapore?

Hi yes you can sure use sidekick mobile in singapore only if it is unlocked one else if the phone is locked to some other network provider in other countries then until you unlock it you can't use it with any other GSM sim .You can easily unlock your sidekick mobile using sites like OnlineGSMUnlock.com they are providing unlock code for all mobile models at reliable cost .You first check that whether the code is available for your mobile model ,country and network provider .If yes then pay for it and unlock your phone .