I think there is a clear connection between carving glyphs on wooden boards in the manner used on Easter Island and the way bamboo was used as a writing material in South East Asia. 

When texts on bamboo in South East Asia were long and more than one piece of bambo needed, they took another piece and continued the text on that. And when the text was completed, they put all the pieces together side by side into something similar to a book. 

The reading of such a 'book' was vertically from left to right. At the end of the first vertical line, the text continued from bottom up on next piece of bamboo, i.e. boustrophedon. 

What is this if not exactly the pattern on a rongorongo board, where the 'book' has been turned 90 degrees to the left? Even the shallow channels sometimes used on the boards might be a remnant from the time the inner surface of a split bamboo was used.