You will not want to pair this with a cleaning out run of the level as that will make it considerably more difficult. Luckily, the method for this only takes a couple of minutes. Select the third mission in the Locksmith's Story (Banque Albert) and choose the Mole as your character.
From the start, back up a step and then start digging through the wall North of you. Dig right once, then continue up/North. This will allow you to tunnel through the second layer of wall in the vault, however for some reason it will not always protect you from the lasers, so as one draws near, back up a few steps until it passes. Continue digging up when it's safe and you'll quickly reach the trophy in the vault. Simply head out the way you came and exit via the train at the bottom of the map.