From Hua Lamphong Train Station, take non air con Bus 29 to Victory Monument, 30 minutes, THB8.

From Victory Monument, take air con Bus 551 to Transportation Center of Suvarnabhumi Airport, 60 minutes, THB34. Take free shuttle bus to Departure Floor, 15 minutes.

Look for Bus 551 under the walk bridge (not under BTS Skytrain Station).

Airport Express Bus AE4 runs directly from Hua Lamphong to Departure Floor of Suvarnabhumi, THB150.

There are also minivans from Victory Monument to Suvarnabhumi Airport. Look at the same bus stop as Bus 551. It's faster as it uses the expressway. The trip takes 30-40 minutes and costs THB45. You may have to buy an additional seat if you have voluminous luggage.

State Railway of Thailand Website

Further Information on Buses from the Airport