Which Pokemon learn thief?

Answer 1

Teach it to a Butterfree with the ability Compundeyes. Compundeyes boosts the number of Pokemon holding items by 50%. Also teach it Sleep Powder, Whirlwind, and Silver Wind/ Bug Buzz. Use Sleep Powder to make the wild Pokemon sleep, then use Thief to steal the Item. If you cant escape, use whirlwind. Silver Wind/ Bug Buzz are just moves to protect Butterfree. You might consider putting a fainted Pokemon with the Frisk ability in the front slot ( Stantler, Shuppet, or Banette). Frisk lets you know if it has an Item or not.

Answer 2

The Pokémon that can learn Thief are Kecleon, Mightyena, Beedrill, Butterfrree, Pidgeot, Raticate, Spearow, Fearow, Raichu, Sandslash, Nidoran Female, Nidorina, Nidoqueen, Nidoran Male, Nidorino, Nidoking, Golbat, Parasect, Venomoth, Dugtrio, Meowth, Mankey, Growlithe, Arcanine, Poliwag, Poliwhirl, Poliwrath, Abra, Alakazam, Machop, Machamp, Weepinbell, Farfetch'd, Tentacruel, Tentacool, Doduo, Dodrio, Dewgong, Seel, Muk, Haunter, Gengar, Hypno, Kingler, Krabby, Voltorb, Electrode, Exeggutor, Marowak, Lickitung, Koffing, Rhydon, Kangaskhan, Tangela, Mr. Mime, Jynx, Scyther, Magmar and Electabuzz.