Thailand - Koh Samui to Krabi Beach

I have done considerable research, but I can't seem to find the right answer or more information. Thanks again for the help;

Do I take the ferry from Koh Samui to Surat Thani and then a bus to Krabi Town?

Or do I take the ferry from Koh Samui to Don Sak and then a bus to Krabi Town?

Also I am looking to take a VIP/1st class government bus, whichever one has the really good seats, is reliable, and comfortable, I seem them called by a variety of names.

Don Sak is one of the ports that handles ferries. It is in the province of Surat Thani but not in the city (meuang) Surat Thani.

There likely are myriad companies operating right from the port but I tend to prefer leaving from a bus station when this is my mode of transit. I just trust the operations from a bus station more.

Any idea how long the bus ride takes and when it departs by chance, most websites don't have recent data?

If memory serves from 8 years ago, the last time I went that route, it was about 3 hours on the bus.