To get from Hat Yai to Langkawi, you can choose various travel routes using a combination of minivan / bus, train and boat via Kuala Perlis in Malaysia or Satun in Thailand.
The journey overland will take you around 6 to 7 hours depending on the connection times at various points along the way.
This is the route we would recommend to take because:
1) It is the cheapest way to travel from Hat Yai to Langkawi (around 250 Baht if you take the cheapest route).
2) Boats from Kuala Perlis are much more frequent and less than half the price of boats from Satun in Thailand (see below).
To get from Hat Yai to Kuala Perlis Jetty to catch a boat, you have a few travel options:
If you are already in Hat Yai, we recommend you take the early morning Shuttle Train from Hat Yai to Padang Besar.
If you are arriving at Hat Yai bus terminal, you can take a minivan service from the bus station to the Padang Besar border checkpoint (they depart every 30 minutes or so - costs the same as the shuttle train).
Once at Padang Besar, you have a choice of travel options to Kuala Perlis Jetty:
1) You can take a quick train journey from Padang Besar to Arau on one of the regular KTM Komuter services.
From Arau you can take a taxi from the station straight to the jetty (a good option if there are a few of you travelling together to cut costs).
You can also take a cheaper local MyBas bus from the train station in Arau to Kangar, then another MyBas to Kuala Perlis Jetty, but if you want to take the bus, you are better off taking the bus from Padang Besar as well (see below).
From Kangar you then take another MyBas to the jetty in Kuala Perlis.
The bus terminal in Kuala Peris is located just behind the ferry terminal and takes just a couple of minutes to walk there.
3) If there are a few of you travelling together, another option is to take a taxi or Grab car from Padang Besar to Kuala Perlis.
Ferries from Kuala Perlis Jetty to Kuah on Langakwi depart from 7 am until 7 pm.
This route to Langkawi from Hat Yai is what you will find on sale at all the travel agents around the city.
It is not the cheapest or quickest route, but as all transport is done from inside Thailand, this is what is offered by the agents.
The first part of the journey is to travel from Hat Yai to Satun.
If you take a local bus, you will end up at Satun Bus Terminal.
From here you will then have to take a songthaew or motorbike taxi to the jetty (about 8 km away).
From the jetty, you can then take a ferry to Kuah on Langkawi Island.
If you buy combination minivan and ferry tickets from an agent in Hat Yai, you will be taken straight to the jetty.
Travelling this route will cost you a minimum of 350 THB as the ferry from Satun is much more expensive than boats that leave from inside Malaysia (even more expensive if you go through an agent).
Currently there are is no direct flight from HDY to LGK, so travelling overland is your only option.