Here is the full list of all 31 Tiny Thief achievements.
Complete 20 levels without using the Hint Book
Gain all the stars on all levels of the 'First Lessons' story
Gain three stars on all levels of the 'Rattling Bones' story
Find all the secrets in the Treasure Chest
Gain three stars on all levels of the 'Bewitched' story
Get at least one star in all levels of the 'Bewitched' story
Gain three stars on all levels of the 'A Royal Rescue' story
Gain three stars on all levels of the 'The Cursed Treasure' story
Use all the doors in the level
Create all types of red candy
Play the piano three times
Take a nap while you hide away
Steal 5 pies
Open the credits screen
Play one level for more than 20 minutes
Get at least one star in all levels of the 'Rattling Bones' story
Get at least one star in all levels of the 'A Royal Rescue' story
Complete 10 levels without using the Hint Book
Find a rat hidden in a chest
Drop 3 gnome statues
Get at least one star in all levels of the 'The Cursed Treasure' story
Complete 5 levels without using the Hint Book
Gain three stars on all levels of the 'A Corrupt Sheriff' story
Get at least one star in all levels of the 'A Corrupt Sheriff' story
Complete 1 level without using the Hint Book
Open the shower curtain 3 times
Pop a bubble gum 3 times
Get at least one star in all levels of the 'A Rumbling Stomach' story
Gain three stars on all levels of the 'A Rumbling Stomach' story
Throw a bucket into a guard's head
Get at least one star in all levels of the 'First Lessons' story