Q. Is the bike suitable for a height of 6 feet person - Dio?

The Honda Dio is not a bike. Being a 6 feet person, i would suggest not. With normal posture your legs will collide with the handles while taking a medium to short turn. To avoid that you need to sit far back than normal. And also the seats are not comfortable. So not suitable for long trips.

Yeah it is I am 5.9 and i dont have any issues but sometimes everyone has different riding styles so you may or may not prefer dio's low slung handle bar because i dont like activas high slung handlebar

U will feel that it's small