Your ping number from speedtest sites, and game ping, will be completely different numbers. Reason, is because when you check on the websites, it picks the closest, fastest server to you, so to reach a server that is just couple miles away in the same, or next city, will be really fast. But if you would to to reach a server across the globe from you, it would take much longer to reach there and back, so ping will be higher. So basically the farther you live from the server location, the higher your ping will be.
To check your ping in the game, when you're in the truck, press [Tab] button, and will bring up a list of all players around you. The first one on the list will be your name, and right next to it will be your ping number.