If you are planning to travel from Penang to Bangkok you have a wide range of travel options to choose from depending on your budget and time scale.
Of course, you don't have to do this trip all in one go and there are plenty of places to stop off along the way if you have the time.
Flying from Penang International Airport (PEN) to Bangkok is the quickest way to travel (duration of the flight is a little under two hours), but the most expensive.
The cheapest flight option is to fly on Air Asia who offers good cheap seats on this route if you book in advance.
They fly from Penang to Don Mueang (DMK), the old Bangkok Airport that now handles mainly budget airline flights.
More expensive scheduled flights are offered by Thai Airways who fly to Suvarnabhumi Airport (BKK).
Another option to check is Malaysian Airlines who do not fly direct to BKK, but sometimes offer good cheap deals via Kuala Lumpur (KUL).
There are no direct bus services that travel this route and you will have to travel between Penang and Hat Yai bus station by minibus or local buses.
Then you can catch either one of the government buses from the bus station on to Bangkok or one of the many luxury bus companies that operate this route from agent offices around Hat Yai bus station.
In Penang you can buy bus tickets from agents under the KOMTAR building (or online here >) that will take you all the way to Bangkok and usually consist of a minibus trip to Hat Yai bus station, then transfer to a bus or minibus for the long leg to Bangkok.
Tickets currently cost around RM 140.
This is slightly more expensive than the train which would be a much more scenic and relaxing way to travel.
From Bangkok you will have to get a bus from Sai Tai bus station (the southern bus station) to Hat Yai, then buy a ticket for a minibus to Penang from the agents located around the Hat Yai bus station or catch a local bus to Padang Besar and cross the border here.
You can then catch a bus or train from here down to Butterworth and then cross over to the island on the ferry to Penang.
The overnight sleeper train from Penang to Bangkok no longer travels to/from Butterworth (since the line has been upgraded to dual electrified tracks for the new ETS trains).
This train now originates / terminates on the Thailand / Malaysia border at Padang Besar.
Connections between Padang Besar and Butterworth are now by the new KTM Komuter (commuter) trains.
The Padang Besar - Bangkok train is an all 2nd class sleeper train that travels overnight in both directions.
For those on a tight budget, another option is to travel to Hat Yai first, then on to one of the trains from Hat Yai that go to Bangkok.
Some of these trains offer really cheap 3rd class seats and 2nd class non air-con sleepers which are not available on the International Express Train.
This may not be the most comfortable way to travel, but it is easily the cheapest way to get from Penang to Bangkok.
You can travel between Penang and Hat Yai by minibus or a series of local buses ( Penang to Alor Setar, Padang Besar and Hat Yai ).
The best way to travel to Hat Yai is to use the new KTM Komuter Trains to get to the border cheaply, then take a local bus or minivan or much less frequent Shuttle Train to Hat Yai.
You could catch a train or bus from Penang to Surat Thani, then a ferry from Surat Thani to Koh Samui, then island hop to Koh Phangan and Koh Tao before coming back to the mainland by boat to Chumphon, where you can join the train again or catch a bus up to Bangkok.
On the way between Chumphon and Bangkok you could stop off at the beaches around Pranburi, Hua Hin or Cha Am.
Another way would be to catch the train to Surat Thani then a bus from there to either Krabi or Phuket before coming back to the east coast at Chumphon.
Penang to Bangkok by Boat / Ferry?
For those that like to travel by boat it is possible to travel from Penang to Thailand via Langkawi using various ferry services.
From Koh Lipe you can then get a boat to Koh Lanta, Koh Phi Phi, Krabi and Phuket and numerous smaller islands in between (some boats only operate during the high season - November to May).
From Krabi or Phuket you can then continue your way north to Bangkok by bus or connect to the train line at Surat Thani or Chumphon.