Here is the full list of all 37 THIEF achievements worth 1,000 gamerscore. It takes around 40-50 hours to unlock all of the achievements on Xbox 360.
Finished the game on Master difficulty
Finished the game with a custom difficulty of 700 points or more
Finished the game without a single kill or knockout
Reached the final chapter without using the focus ability
Finished 3 consecutive chapters without taking damage
Scored an epic 5,000,000 or more in a Challenge Map
Discovered all secret areas
Shot a bottle in mid-air with an arrow
Completed all collectible sets
Used 40,000 gold
Completed 25 optional Thieving Objectives
Picked a pocket and a lock using the focus ability
Completed all client jobs in The City
Stole all loot and collectibles in a single chapter.
Completed a collectible set
Finished the game in 15 hours or more
Finished Chapter Eight
Finished Chapter Seven
Completed all Basso Jobs in The City
Picked 100 pockets in a single playthrough
Finished Chapter Six
Completed 10 optional Thieving Objectives
Finished Chapter Five
Disarmed ten trap mechanisms
Found all the secret stashes in Moira
Picked a lock with masterful speed
Discovered 15 secret areas
Finished Chapter Four
Finished Chapter Three
Killed or knocked out 10 people using the environment
Finished Chapter Two
Stole 5 collectibles
Sweet sixteen. Snuff said.
Finished Chapter One
Finished a single chapter without alerting anyone
Uncovered Lyegrove's secret
Finished the Prologue