A risky undertaking, it will take years and years to build and
at huge cost overruns, and they will have to deal with a lot of
protest.
Protest from wildlife preservation groups, protest from greenpeace
groups, protest against loss of habitat for certain animals or even
some aquatic sea mammals, protest against loss of land rights of
certain ethnic minorities, protest from ecological rights groups,
complains against corrupt government officials trying to line their
pockets.
Then there is the unrest in the south that might sabotage the
project in a bid to preassure central thai government to allow self
rule in the south. Or they may even see it as the government trying
to "annex" their land thereby paving the way for ethnic
migration(like indonesia) to other parts of thailand forcing them
to disperse which will may make them even more determined to
undermine the project.
Then there's malaysia who might not be very happy since more
shipping now goes thru thailand kra canal and may even start
levying "special taxes" for all cargoes that cross into overlapping
malaysian waters is one possibility.
Another possibliity that during the early clearing and digging of
the canal and construction on the west coast it may cause water
levels in the tight straits to drop making it dangerous to heavy
ships to pass thru causing security problems, huge delays for
merchants shipping resulting in losses of billions.
in the end it will cost both legs and arms of many thai
presidential administrations.