Mightyena
Keckleon
Poocheyana
Lombre learn thief upon leveling..and
All the pokemon can learn thief using the TM
I think you cant catch a Pokemon that learns thief, without the use of the TM. Alot of Pokemon can learn Thief through TM, but i don't know where to find the TM in the games. I did, but i fogort, sorry. Maybe check bulbapedia?
You are not able to buy the TM for the move Thief in Pokemon Platinum. You can find the TM for Thief in Eterna City. The move Thief isn't use often competitively and it doesn't matter which Pokemon can use it for it to steal held items.
You can find TM Thief in Mahogany Town in the Rocket Hideout
number 46
in your bag where eles
Poocheyna and Kecleon.
If the other pokemon has an item and you don't, you get that item.
mt moon
TM46 Thief is located in Mahogany Town Hideout.
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.
You can find TM Thief in the Oceanic Museum in Slateport City. There should be a Team Aqua member standing inside the museum. Talk to him and he will give you TM Thief.
Near the Eterna Galactic Building.