I think its the same region as the Andaman Is. They use very wide flat bows, sometimes have a weird side profile where one limb looks reflexed and the other looks deflexed. These bows don't appear to have that configuration.
I don't think these would be black palm, as palm bows are almost always long and narrow. I couldn't say what timber they have used, but almost any reasonable hardwood will make a bow when wide and flat.