I don't see any errors. Its a fairly weak card though, they've no auxiliaries to escort. Perhaps trade guard the convoy for guard the flotilla? Or costal tactics (concealment at r2>)
Chonburi already has Coastal Tactics. These poor Thai/Siamese ships have every coastal SA in the book.
What about?
Evade Torpedoes - Once per game, when an enemy unit makes a Torpedo attack against this unit, roll a die. On a 3 or higher, the attack misses. This unit can't move during Sea Movement the turn after it uses this ability.
or
Good Luck - When this unit would be hit by a Torpedo attack from an enemy Submarine, roll a die. On a 4 or higher, the attack misses instead.
or
Lucky Escape - When this unit would be hit by a Torpedo attack from an enemy Destroyer or Torpedo Boat, roll a die. On a 4 or higher the attack misses instead.
Lucky Escape seems appropriate and useful to me.
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