If you want to travel from the Malaysia-Thailand border at Padang Besar to Krabi there are no direct transport options, so the first step of your journey will be to travel to the nearby city of Hat Yai.
How you go will depend on how you want to continue your journey to Krabi.
If you want to go by bus, the best option is to take a local bus or minivan from the Thai town of Padang Besar to Hat Yai Bus Terminal >
If you want to travel to Krabi by minivan or train you should take the Shuttle train to Hat Yai Junction Railway Station >
Regular buses depart from Hat Yai Bus Terminal (although you do get the odd departure from the city centre, these are usually fairly expensive luxury coaches costing 400 Baht+).
This duration of the bus journey to Krabi is approximately 5 to 6 hours and cost from around 200 Baht to 400 Baht depending on what type of bus you take.
Slightly quicker but more expensive than a bus, minivans run regular departures from Hat Yai to Krabi Town, Ao Nang and Railay
You can buy tickets for these minivans from dozens of places in the city and bus terminal but prices can vary quite considerably (so shop around to find a good deal).
A minivan to Krabi should cost between 250 - 350 Baht.
A popular (and fairly honest) place to get a reasonable price is from the travel agent at the popular Cathay Guest House a couple of blocks down from the train station (on the right).
Although it is possible to travel part of the way from Padang Besar to Krabi we would not recommend you take the train past Hat Yai as this is where you will find the best connections to get to Krabi.
You could get bus connections from Phatthalung or Thung Song Junction stations further north, however, the bus stations at these places are a long way from the train stations on the main highway (so you will need to take quite a long motorbike taxi adding to your costs).
Currently, there are no direct flights from Hat Yai Airport (HDY) to Krabi Airport (KBV).