The Latts Razzi Crew says:

When defending, you may remove 1 stress token from the defender to add 1 evade result to your roll.

If the attacker has multiple stress tokens, can the defender remove more than 1 to add multiple evade results? There doesn't appear to be any restriction such as, "once per attack".

No, you may only remove 1 stress token, as per the card text.

Why not more you ask?

Page 8 of the Rulebook under Card Abilities

The Latts Razzi Crew says:

When defending, you may remove 1 stress token from the defender to add 1 evade result to your roll.

If the attacker has multiple stress tokens, can the defender remove more than 1 to add multiple evade results? There doesn't appear to be any restriction such as, "once per attack".

But there is restriction clearly stating a single token - token, tokens - singleton not plural.

Yep. If it was intended to work differently, the card would be worded something like:

"... you may remove any number of stress tokens from the defender to add the same number of evade results to your roll."

If 2 different stressed ships attack you; however, you can use Latts on each ship's attack to add evades.

And with a TLT, you could trigger it on both rolls if they have sufficient stress.