Something has to be done. The short term looks bad, a sea barrier is medium term, a new city looks best for the long term.
The Chinese construction teams would make a good job of this and would put money in if it is part of BRI.
Learn from Neom https://en.wikipedia.org/wiki/NEOM.
Where is the tourist authority? Why aren't they defending their patch? That's three months revenue lost every year in certain parts like chiang mai, which depends on tourism