For me the arrows in the quiver are not made for a blowgun but for a crossbow and look very much like the arrows of crossbows from "Montagnards" or "Moļ people" ( = all tribe from the central hightland of Vietnam ).
On this link you can see many crossbows and some bamboo quivers.
http://www.croiseur-lamotte-picquet.....php?page=mois