Note that the completion of the outer ring road, including the new southern bridges over the Chao Phraya, have made access to Suvarnabhumi much easier from the Klongsan side of the river, particularly down by the Marriott. Rather than taking Taksin Bridge to the Expressway, you can go south or west to pick up the ring road and take that clear to the southern entrance to Suvarnabhumi from the Bangna-Trat Elevated Tollway. The entrance ramps are not finished yet, but you can still get into the airport that way on the surface roads.