This is my Ayutthaya-era dha. The Ayutthaya Period ran from 1350 to 1767, but we are pretty sure that these are from the mid-Ayutthaya Period, i.e., 16th-early 17th C. AD at the oldest. I say 18th C. on my website, but we've since gotten information from one of the early owners of the blades that pushes the date further back.
The whole page on it is
here.