From the little we do know from murals and scuptures it seems that in Bagan ( Burma 11-13th Century ) swords were 2 edged and not single edged like the dha we know and love .
Here are some photos from Illinois University of Nat statues from Bagan. ( nat depictions usually always have them carrying a single edged dha ) with a doubled edged sword.
Here are some links to movie posters of KyansittMin ( the film about Kyansittha a king from that era ) featuring a double edged sword .
poster 02
poster 03
poster 04
I thought it might be of interest to the dha ethusiasts on this forum and begs the question about when the single edged dha appeared on the scene .