Hi Marc,
Sorry for my late reply! Your dha/daab is a Siam/Thai daab. The inscription on the coin is Thai, there is also a date visible.
Date on coin: ๑๒๔๔ (1244: Chula Sakarat) = 1882 (Gregorian calendar).
The Chula Sakarat calendar was used in Siam during 1835-1887.
It's a very nice sword, if you ever get bored by it, please let me know!
Best regards,
Detlef