I feel very sad about this and feel for those that experienced it. The people affected must be in shock. Imagine those in high rise buildings. That experience would be a nightmare. For those that died RIP and for those that were injured I hope you have a quick and full recovery. For the rescuers you are brave.
I have never experienced an earthquake and never want to. I have seen the effects of one in Christchurch NZ, magnitude 6.3, just before and 6 months after. It happened in 2011 Christchurch was built on swamp land similar to Bangkok. There were 185 deaths and thousands injured, which is a large number as the population was no where near Bangkok's population. In fact they were thinking of moving the city. Earthquakes are very rare in NZ. The last major one was 1855.