lv 1
A keckleon in the wild already noes thief.
Poocheyna and Kecleon.
Kecleon and Mightyena learn it while leveling up. Almost every other Pokemon can be taught the TM thief.
The Pokemon that can learn Thief are listed at this site: http://bulbapedia.bulbagarden.net/wiki/Thief
Clefable cannot learn thief at any level, not even from the TM. However it may use Thief if it knows Metronome, or a similar move.
Well, starly (or staravia) will eventually learn thief when leveling up. Personally, I I think Thief is a useless move.
Mightyena and Kecleon by level up there is so much by TM so ill just list the website http://www.serebii.net/attackdex-dp/thief.shtml
many Pokemon can learn thief. i taught it to my bronzong and magnezone
dark Pokemon can on learn thief in firered
Mightyena Keckleon Poocheyana Lombre learn thief upon leveling..and All the pokemon can learn thief using the TM
i think staraptor can
Keckleon Mightyena and oall the pokemon learn using a TM.