You have several options for transferring between airports in Bangkok. The best way to travel from Suvarnabhumi Airport to Don Muang Airport depends on your needs as you can get from BKK to DMK airport by shuttle bus, public transport, taxi or private transfer.
Free Shuttle Bus between Bangkok Airports
If you will be landing at Suvarnabhumi Airport (BKK) and will have a domestic or international flight from Don Muang Airport (DMK) on the same or next day, you can use the service of shuttle bus between Bangkok Airports. This shuttle bus is offered for free so it's by no means the cheapest way for getting from Suvarnabhumi to Don Muang.
Shuttle bus from Suvarnabhumi to Don Muang starts operating at 5:00 and the last bus leaves at midnight. Expect the shuttle bus to depart every 12 to 30 minutes, depending on the time of the day. The trip from BKK to DMK can take anywhere from 50 minutes to 2 hours, depending on traffic conditions.
Free shuttle bus departs from the 2nd floor of Suvarnabhumi Airport (Arrivals Level), outside the door 3. At Don Muang Airport passengers are dropped off at the upper floor (Departure Level).
Detailed information about the shuttle bus can be found here: Free Shuttle Bus between Bangkok Airports.
Public Transportation from BKK to DMK
If you don't have a ticket for a flight departing from DMK Airport on the same or next day, your cheapest option to get from Suvarnabhumi Airport to Don Muang Airport in most cases is by using Bangkok public transport.
There is no direct train connection between Bangkok Airports so far. If you want to travel from BKK to DMK by public transport, you need to take Airport Rail Link train first and then transfer to one of the shuttle buses serving Don Muang Airport. In general, you have three decent options for a transfer between the airports by public transport.
Option 1 - Airport Rail Link & Bus
At Suvarnabhumi Airport, you need to go down to "B" level where the station of Airport Rail Link is located. Detailed information about finding the train station at the airport can be found here: How to Take Airport Rail Link Train from BKK Airport. The airport train operates from 05:30 to midnight.
From the airport you need to take the train to Ratchaprarop station. The journey by Airport Rail Link from Suvarnabhumi Airport to Ratchaprarop station takes about 25 minutes and costs 40 THB.
Travel SMART! Book your Airport Rail Link ticket online & don't waste your time at ticket vending machines as the queues at BKK airport can be long
From Ratchaprarop station you can take A3 Bus to Don Muang Airport. Bus ticket costs 50 THB.
Option 2 - Airport Rail Link & MRT & Bus
Take Airport Rail Link from Suvarnabhumi Airport to Makkasan station. The journey by Airport Rail Link takes about 22 minutes and costs 35 THB.
Here you need to transfer from Makkasan Station to MRT Phetchaburi Station. It's easy because these two stations are connected by a skyway. Check how to transfer from Airport Rail Link to MRT.
Then you need to take MRT Metro from Phetchaburi Station to MRT Chatuchak Park Station. The journey will cost 33 THB.
From the bus stop near Chatuchak Park you need to take A1 Bus or A2 Bus all the way to Don Muang Airport. Bus ticket costs 30 THB. Detailed information about transfer from MRT to DMK shuttle bus can be found here: Bangkok A1/A2 bus from MRT/BTS to Don Mueang Airport.
Travel SMART! Get a discounted Thailand SIM Card at the airport and use unlimited Internet on the way: [SALE] 4G SIM Card for Thailand (Airport Pick Up)
Option 3 - Airport Rail Link & BTS & Bus
Take Airport Rail Link from Suvarnabhumi Airport to Phaya Thai station. The journey by Airport Rail Link takes about 30 minutes and costs 45 THB.
Travel SMART! Book your Airport Rail Link ticket online & pay less than you would pay for a trip to Phaya Thai station
You will need to transfer Airport Rail Link Phaya Thai Station to the same named BTS SkyTrain Station that is found nearby.
Take the train from there to BTS Mo Chit Station and drop off there. The journey will cost 37 THB.
Be noted that all DMK shuttle buses start operating from 7:00 and are not suitable for early morning and late night transfers!
Taxi from BKK to DMK Airport
The distance between BKK and DMK Airports is about 46 km. The journey by taxi from Suvarnabhumi Airport to Don Muang Airport should cost about 400-500 THB, not including toll fees and airport surcharge.
For getting such a rate you need to make sure that taxi driver turns the meter on. You should never agree on a fixed fare as it will be a rip off.
Private Transfer from BKK to DMK Airport
If you are looking for the most comfortable way to transfer between Bangkok Airports, book a private transfer online and the driver will be waiting for you at Suvarnabhumi Airport holding a sign with your name on it. It's definitely the most comfortable way to get from Suvarnabhumi to Don Muang as you won't need to travel by crowded public transportation and won't be ripped off by taxi drivers.
Private transfer from Suvarnabhumi Airport to Don Muang Airport can be booked here: Private Suvarnabhumi Airport Transfers (BKK).
How to travel between Bangkok airports the other way? Check here: DMK to BKK - Don Muang Airport to Suvarnabhumi Airport.
More information about other facilities at the airports can be found here:
Book a discounted Thailand 4G SIM Card and pick it up at the airport: [SALE] 4G SIM Card for Thailand (BKK or DMK Airport Pick Up).
Flight deals to/from both Bangkok airports can be found using the form below.
Check our Frequently Asked Questions about public transportation in Bangkok and ask your own question if it's not answered there yet.