Is it possible?

yes...unless we do something.

I read that rising sea levels will affect mosly Bangkok and areas of Trat.

Hmm I also heard about this global warming and sea rising level story is spread by those oversea investor to dump the land price which near by the sea down.
They want the land near by the sea cuz it is very value. These land are good for factory hotel and farm.

Where will it divide?

Yes that's true about global warming and that's what some investor do here in my country. They would build high rising hotels and establishments near the sea. Taking advantage of that sea rising level situation. I wonder how long would it stay solid knowing that it was just a manmade land dumped with soil.

I can see the Central Thais trying to move into Lanna or Issan territory. Hopefully those areas would receive the help that they deserve(mainly issan) and flourish with wealth like bkk once did.

So we should walk to work and stop those factory to hurt the mother of earth right? Plus dare tell your boss to turn the aircon off the aircon in the office to safe the world.

Hmm the area that was the central Thailand Ayudhaya Bangkok ,Nonthaburi province was under the sea level before. The picture above shows the pagoda which built from the salt water shell in upper Bangkok province.
So that it could be posible that they would sink again.

But thanks to many of the dam that was HM project ,without that Central Thai would suffer from flood every years