The base Sneak Attack rule still applies

Thief does not add a new way to qualify for Sneak Attack. Instead, climbing, stealth, object use, and positioning help the Rogue create the circumstances for a normal qualifying finesse or ranged weapon hit.

Subclass interaction

Thief does not add a new Sneak Attack condition. Its advantage comes from positioning and action economy: climbing, stealth and Fast Hands can help create a strong firing or melee position while leaving the action free for the qualifying Sneak Attack weapon attack.

Reaction attacks can still matter

The subclass does not consume the reaction heavily at low levels, so opportunity attacks remain useful off-turn Sneak Attack opportunities. At higher levels, the main action-economy change comes from Thief's Reflexes rather than from a new reaction feature.

Do not double-count subclass damage

Fast Hands and Use Magic Device can create additional effects through gear, but those effects are not automatically part of Sneak Attack. Resolve the weapon attack and Sneak Attack separately from any item effect unless a specific item says otherwise.