Although I have never been a believer of the huge danger of dengue fever (or malaria for that matter) in Thailand I think you should be aware that both arre still a threat to your health in Thailand. There is a minor problem, many times when someone is sick it is called "Dengue Fever" on basis of symptoms only. No blood test done. And people then not get really sick, so many people not really worry about Dengue Fever. But you should as without proper care it can kill you!
A friend of us living in Chonburi has been diagnoses with dengue fever. Although as far as I know also only on symptoms. But the symptoms were so clearly and strong that even I (and I am not a doctor) would say "dengue fever". Our friend did get sick and at first thought "little bit not well" and took some home medication. But after a few days the high fever did not go away and our friend was hospitalized. There was quickly thought of dengue fever and our friend was getting supportive management. Mind you, server cases of dengue fever can be fatal. Especially without the correct supportive management. Our friend thought to have been infected with it while on a few days holiday tour in Chantaburi, but due the incubation time I would say it could as well have happened at home in Chonburi.