That's a 20-40min drive depending on traffic. I was a first timer to BKK in Dec 06. Took 5 Sukhumvit-ish to airport taxi rides during my 3wk stay. No problems. Paid 300baht plus/minus 50. For reference, hotel "limo" was 2000. To undercut that, Fodors has good references for a few drivers in BKK. Search for "Ratt". I hired her sister in Chang Mai. They are good people.