Is there any subway from GuangZhou High Speed Rail Soth Station to Foshan City Centre? Cost ?

There is no direct subway line from the south railway station to FS city, but you can transfer twice to reach that place.
From the south station, you can take the Guangzhou subway line 2 to get to Gongyuanqian Station where you can change to subway line 1 to get to Xilang Station. From Xilang Station, you can take the Guangfo line to get to Zumiao Station or Kuiqi Road Station, which are two main places in FS and then take a taxi to anywhere you want to go.