I didn't manage to snap a picture before the door obstructed the markings, but it said SK-GWT. It's a railbus they bought in Slovakia. Old friends meeting again.
@pony If we would have that good looking buses like that.
@RealPurrplenekoboi it's just the class 810 railbus with some small interior improvements. You can find this thing on local railways in CZ, SK and even HU.