I haven’t seen Thai stuff recently but your description sure sounds
like standard plating procedure. Copper flash for bond, bright nickel
build up to make smoother, and a top flash most likely fine silver.
Heat it and the nickel does really bad things.
It is possible to strip all of the plating leaving a frosted silver
surface but the extra work involved I only used for rather expensive
repairs. As I remember 40% H2SO4 with a lead Cathode (bass-ackwards
from plating) and about 6 volts, lots of amps. There is a better
description in an old post of mine in the archives, or I can dig out
my reference book with the exact details.