I conclude that a palanque is a 'stand, covered platform, stage'. There are other terms in English (dais, tribune, rostrum, bleacher) but each of these is qualitatively different in some way or other.
It appears that palanque is a sort of augmentative derived backwards from palanquim 'covered litter for one passenger', a loanword of Goan origin. Obviously the covering or roof is the key element linking the two terms, and it is for this reason that stand seems to me to be the nearest translation.
[Edit: If the structure is intended for speakers rather than important onlookers, then it may be referred to as a stage or platform rather than a stand.]