It is difficult to know the reasons why tourism to Bangkok has dropped so much in just one year. Probably have many reasons, some maybe that politics from the past cause people to be unsure about safety in Thailand. Another reason maybe the traffic is so much that Bangkok become more difficult to travel easily. Or maybe many people that travel often have been to bangkok already and have become more interested in other places that have more culture and nature compared to Bangkok. The other cities on the list seem to be cultural places with long history and maybe that is something people think Bangkok has less after the city become more modern.