If there are changes in your route, make sure you always have enough time to walk from one platform to the other and never forget the possibility of delay that could make you miss the second train.
When travelling on such short distances, you can take into account also busses and carpooling options: with some luck you will find very cheap options, even if you book on short notice.
In which stations can you take the train to Surat Thani and where will you arrive?
Trains leave Hat Yai from ชุมทางหาดใหญ่ and arrive at สุราษฎร์ธานี.
How long will it take you from Hat Yai to Surat Thani by train and when do the trains leave?
With the fastest connections you will be in Surat Thani in 4 hours and 8 minutes, but on average it takes 5 hours and 36 minutes. The first train headed to Surat Thani is at 06:11, while the last one leaves Hat Yai at 18:11.