As was said, few Burmese can afford reasonable preparations, be it a boat or backpack of food.

Evacuation may not have been practical anyway: I don't think the area has the infrastructure in terms of rail or road, train or bus.

And their problems are only beginning. This was the primary food production area in Burma and it has just been substantially inundated by salt water. Rice exports from Burma have been falling from 4 million tons years ago to under 40,000 tons now, which implies that even before this the country was barely able to feed itself.

And speaking of salt water inundations ... the satellite images suggest the salt water spread well inland. What will they drink?

I suspect that living inland and farming on the coast is not realistic. Transportation is a luxury there. I doubt many third world farmers can afford to living beyond easy walking distance of their field.