As most people are not professional racers its prudent to keep within speed limit. If one must go above the speed limit it better that he is familiar with the road he's traveling on for example he knows where the curves and convergence of lanes are and even time of the day traffic is high etc.
Every morning on my 42km way to work I will pass by a stretch of 9km along the end of Ekkamia Ramintra highway, this is a 3 lanes tollway and very few cars every moment of the day and as I am very familiar with this I will drive between 150km/h to 190km/h every morning without fail. But after that when connected to the Outer Ring Road (Kanchanaphisek) I will be a good boy and slow down to 120km/h as there's more vehicle. If anyone of you come to Bangkok and drive its worth to come to this stretch and experience driving fast. One a while can see super cars there zipping past you.