Is there a direct bus from Sungai kolok to Surathani Town? Where does the Bus stop in Surathani Town? Thanks

I doubt you will get a "direct " bus .What you will get is a Bangkok bus that will stop at Surat Thani. Your better bet is the train ,I suspect. Check with the railway station.It is quite a nice trip, by train, but will maybe be slower than the bus.

There is also a daily bus that runs direct from the ferry pier at Donsak to Sungai Kolok and return (overnight). If of interest I can find times and cost.