If you want to travel from Sungai Petani to Thailand by train, you will firstly have to take a KTM train from Sungai Petani to Padang Besar Railway Station, located just inside Malaysia on the Thai border.
The easiest, cheapest and most regular trains services to the Thai border are operated by KTM Komuter (commuter) services.
These commuter trains operate throughout the day every one to two hours and take just over an hour and a quarter to arrive at the border.
The fares for these Komuter trains are much cheaper than the ETS services at 9.30 MYR for a one way ticket.
These trains however do no guarantee you a seat as the trains are subway / tube train style and no reservation is allowed.
Tickets are only sold on the day of travel and during busy times there may be only standing room available for some or all of the journey.
Please Note: If you are planning to cross into Thailand, the immigration at PB station closes in the afternoon after the last train leaves for Hat Yai / Bangkok.
If you arrive later, you will have to use the main land border crossing which can be reached by a walkway over the railway tracks (walk upstairs from the platform).
This border is open until the late evening, but local buses to Hat Yai from the Thai side stop at around 18:00.
So - plan to cross over to Thailand in the afternoon and don't get there too late!
If you want to travel in your own reserved seat you will have to take one of the more expensive ETS trains from SP to Pdg. Besar.
Tickets for these trains cost:
23 MYR for ETS Gold services.
29 MYR for ETS Platinum services.
These trains are slightly faster than the Komuter services as they stop at fewer stations.
All ETS Trains heading north to the border stop at Sg. Petani.
As mentioned above, if you decide to travel by Komuter Train you can only buy tickets for these services from the station on the day of travel.
For ETS Trains, advance booking is always recommended.