Does Traveling Merchants draw trigger before the Tank ability?

Yes, the Traveling Merchant's ability triggers and resolves before the Tank ability becomes relevant.

Here is the breakdown of why:

1. Traveling Merchant's Ability: This is a triggered ability ("When I move..."). When the Merchant moves, this ability is placed on the chain and must resolve.
2. Tank Ability: This is a passive ability (Rule 741.1). It does not trigger or use the chain; instead, it functions as a continuous rule that modifies how combat damage is assigned during the Combat Damage Step (Rule 443.1.d).

Sequence:

• Movement: The Traveling Merchant moves.
• Trigger: The Merchant's "When I move" ability goes on the chain.
• Resolution: The chain resolves, and the Merchant's controller discards one card and draws one card.
• Combat: Only after the chain is empty and all triggers have resolved does the game proceed to combat (if applicable).
• Damage Assignment: During the Combat Damage Step, the Tank ability is then applied to determine the order in which damage must be assigned to units.

Because the Merchant's ability is a trigger that resolves on the chain and Tank is a passive ability that only applies during the damage assignment phase of combat, the Merchant's effect will always be finalized long before the Tank ability influences the game.