No, it’s not necessary. But it is okay to let the monk’s chant prayer of blessing over
the amulet’s for purify, or do you have any idea that having the brief blessings to
the amulet’s could really recharge it power?
Usually we saw people’s taking off their amulets and let the monks chant and bless
when they go to the Thai temple on their holiday to pay respects to the monks.
The brief blessing is usually a general blessing for all amulets and not for the particular amulet itself. The Monk or Archan who create the amulets will only know
the special knowledge to bless the amulets that they created.
(When one visiting the temple I believe that no monk will ask for your amulets for
blessing “unless you handed it to them”, or they will only blessed you and sprinkled
holy water on you to bring you luck).
However, if your amulet have been touched by someone else’s, it might be good
for you to take a ritual bath to purified the amulet over an incense smoke.