They are Sinkholes. According to http://library.thinkquest.org/CR0215689/sinkwhat.html; "A sink hole is the erosion of land. It forms when underground water dissolves minerals in the ground. This creates a buried hole. Eventually, the hole becomes large enough that the land on top caves in. Sinkholes are common in land containing limestone, because limestone is soft and has water holes like a sponge. It also dissolves in water." (See picture 1 for an easier understanding)
picure 1.
However, though Bangkok is not located in limestone areas like those provinces mentioned above, it is still in the risk of having one (or more) because this terrible disaster is also caused by human, from pumping up groundwater for people's consumption.
Phra Nakhon side of Bangkok (around the Temple of the Emerald Buddha) use to be canals in the early Ratanakhosin era that even people from the west use to call Bangkok as the "Venice of the East!" But when westerns came they also brought their technology and knowledge with them. Economy became more important than tradition, ROADS became more important than canals. That is why the government of Siam piled up the canals and make them as streets for cars and convenient transportation system. Though time passes the canals are still there underneath the streets of Phra Nakhon. About a century after, the population growth rapidly increased also the need of water consumption. Since people know that underneath Bangkok lies a large source of water, they pumped it up for their, also, our, consumption. By doing so continuously, the groundwater source decreases. This will cause the constructions in those areas to slowly collapse. But at this time of total disaster and the stimulation from climate change, things may be worse than we could imagine. Just like in Guatemala, the roads of Phra Nakhon could possibly be like picture 2.
picture 2
Is there anything we could do to fix the past? How about trying to find a solution and protection for this.

