This requires a bit of patience if you are really watching the pennies, as most touts will promote a ‘special offer’ of around 500THB. However, it is possible to find a taxi ‘on the meter’ at Bangkok International Airport to take you on the 45 minute journey into the city for around 300THB (about £6.25/$9.62). On good days the total price on the meter has been under 270THB!
The best way to do this is to head to Departures, as there will be taxis here who have just dropped someone off, and will be heading back to the city anyway. They are the most likely to accept the meter fare.
They will expect you to pay the two toll fees on the way so make sure you have some change. The total cost of taxi & toll fee will still be less than a fixed price, which is often 400-600THB.
Throughout Bangkok you will see many fuchsia pink taxis, which are very famous! Look for them. They also have taxis that are red and yellow, which look a bit old-school, but all legitimate taxi drivers will have a licence set inside the left of the windscreen, which is most important especially if traveling alone.