If they are considered a weapon they wouldn't be allowed in your backpack any more than they would as a necklace. Doesn't matter where they are, they still have to go through the x-ray. Having said that, I can't imagine security in any country considering them a weapon.
BTW, your mileage may vary, but Air Asia isn't known to be too strict on the carry on weight. You can probably put everything in your backpack and not worry about it. I can't imagine wanting to double layer clothing anywhere they fly, pretty much a hot part of the world.