I have been "lurking" now for quite some time.  Finally, I feel I have
something to add.  Having lived in Thailand for 2 years, Mary, I
believe
the coconut "huts" as you call them, are young coconuts, the husks
trimmed to look like a hut.  It should have a top (roof) that can be
removed.  The inside is simply eaten with a spoon.  It tastes very
good
on a hot day in Bangkok.  As for how long it can be stored, I am not
sure.  They are usually eaten quickly.  I would assume if it is still
white, smells good, it can be eaten.
Donna