A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Storm-Filled Sails has the Thunder keyword, so it's Limited ability obviously is a Thunder action. Is the Battle ability granted by the card also a Thunder action? My guess would be yes, but I'd like confirmation on this.
Strategy Storm-filled Sails Thunder Limited: Until the turn ends, you have the ability, "Battle: Attach a target attachment from your hand to your target Personality. If this attached a card, draw a card." Gold 0 Focus 3
Storm-Filled Sails has the Thunder keyword, so it's Limited ability obviously is a Thunder action. Is the Battle ability granted by the card also a Thunder action?
No.
The ways an action can have a keyword are listed in http://rules.l5r.com/CE_Card_features#Abilities. "An action permitted by an action generated by a card by with a keyword" is not one of them.