Yes, buses and coaches up to 3.5 tonnes need an e-vignette if being used on Czech toll roads.
Vehicles with a maximum permissible weight of over 3.5 tonnes (incl. combo of vehicle + trailer) use a distance-based toll system (MYTO CZ) instead of the e-vignette.
Related articles:
What vehicles need a Czech e-vignette?
Do trailers and pulled caravans need separate Czech e-vignettes?
What is the MYTO distance based toll?