The easiest way to reach Suvarnabhumi airport, which is the main Bangkok Airport with call letters BKK, from Khao Sand Road, is to first make your way to the Phaya Thai BTS / Airport Rail Link station to ride the train from Phaya Thai Station to Suvarnabhumi Station. The entire ride on the train takes around 26 minutes, costs 45 baht and you arrive on the underground level of the airport itself.
But, before you can take the train you first need to make your way from Khao San Road to the Phaya Thai Skytrain Station. Since Khao San Road is located in the Old City and is not connected to the city’s train network you are left with few options. It is about 5.5KM, so on foot you’d have to hoof it for about an hour. With luggage and all, that should be reserved only for the elite urban mercenaries of budget backpacking hell bent on saving a satang everywhere they can. For the rest of us with our wits about us, we will opt for a vehicle of sorts.
The cheapest option is Bus #503 leaving from Kong Salak bus stop on Ratchadamnoen Road. Look out for the red bus as it costs no more than 8 baht. Catch the yellow bus that is air conditioned for about 12 baht, or the orange air conditioned bus for around 18 baht. Each of these buses should operate with some consistency, however be aware that waiting on a certain color of bus #503 could cause significant delays to your journey.
An alternative is to grab a taxi. A metered taxi is difficult to find around Khao San Road itself, so try walking over to the main road of Ratchadamnoen to flag a taxi driving by. These taxis will be more likely to use the meter. A metered taxi starts at 35 baht and goes up about 6 baht per kilometer. Your journey from Khao San Road to Phaya Thai Airport Rail Link Station shouldn’t exceed 75 baht with smooth traffic.
If you are unable to find a metered taxi to take you, try your luck with convincing the nearby tuk tuk drivers or taxi drivers to ride you at a flat fee not more than 100 baht. A motorbike taxi should take you for 60 or 70 baht.