You could start by looking for these Pendant King Thailand Rama 5 Yant Thai Amulet Talisman Fortune Protect life
Its a restrike of a pretty famous medal. Even the originals were medals, not coins, struck during the reign of Rama V. My way to spot restrikes from originals is to concentrate on the riders of the elephants. Restrikes have them in pretty low relief, no details of hands, etc. The originals are much sharper. Going off of memory, but believe around 1880ish the originals were struck. I am sure someone can correct this and give the exact date. Edit: Here is a listing for an authentic example. Notice the details on the riders. This medal is very common in Thailand and still sold today, (as authentic to tourists). https://www.spink.com/lot/CSS28000994