A nice one!
I think it's a Lawi Ayam, Korambi etc...
Some of them have an open "half ring", like yours, as a finger rest.
Most of them have closed/full rings at the top of the hilt for fully inserting a finger.
My Silat teacher's wife is very good with them and they can be a very nasty surprise and are difficult to disarm.
The reason it looks like a Beladau is because it's local variations of the same weapon - the Jambiya.
But the size of yours, as well as the blade shape, indicates a Kerambit, Kuku Ayam, Kuku Rimau etc...
Actually I think it's many names for the same knife but maybe someone else can enlighten me if there is a difference?
Michael