If you would like to travel on the Penang Surat Thani Train service from Butterworth railway station, the one direct train is now no longer operating from Butterworth, but now originates from the Malaysia / Thailand border railway station at Padang Besar.
Your first step of the journey now involves taking a cheap KTM Komuter train from Butterworth to Padang Besar.
You can then connect to train number 46 (International Express) departing for the overnight journey to Bangkok (stopping at Surat Thani station).
This train is an all 2nd class A/C sleeper train so you have buy a ticket for a sleeping berth, so it is not the cheapest way to travel from Penang to Surat Thani.
Also please note that the Surat Thani train station is not actually in Surat Thani.
It is located around 15km outside of the city at Phun Phin, so you will have to catch a local bus or taxi to the pier for boats to Koh Samui island or buy your ferry tickets from an agent where the bus transfers will be included.
Another option to travel from Penang to Koh Samui would be first to travel from Penang to Hat Yai by minibus, then catch a frequent bus or train from Hat Yai to Surat Thani.
The minibus can drop you off at the bus station or train station in Hat Yai.
Please see the following pages for more information about onward travel from Hat Yai to Surat Thani, Koh Samui and Koh Phangan.
Alternatively, you could take a Komuter train to the border.
You can then walk over the land border crossing and catch a local bus to Hat Yai bus station or into the city centre.
Then continue your journey by either bus or train from Hat Yai to Surat Thani.