The picture above is my wrist with string tied on it. In Thailand on special occasions like birthdays and weddings, a common tradition is to give wishes in the form of string. The person rubs the string down your wrist while making the wish, then ties it around.
In a large village a popular person can end up with an armful of these string loops. The tradition is to keep wearing them till they come off on their own, but it's enough to keep them for at least 3 days. They're usually too tight to remove, and so you keep them on when you shower, so the string breaks down quite quickly.
When you get married, the bundle of string is kept, just as you'd keep your wedding dress. It was the wishes for a happy marriage.