I might have been lucky as I was told the fare needed to go from my hotel to the airport would be at least 400-500bahts. I have heard how my friend who went to the exact same hotel just a few weeks ago had to pay more than 400 bahts. He considered the price to be good because he had earlier paid touts 1,000 bahts to travel from airport to the same hotel.
Actually I do not know why it is more expensive to travel the same distance but it seems that going from Bangkok city to airport is cheaper than the other way around. One thing, the 50 bahts surcharge by the airport taxi counter makes the going more expensive.
I got into the metered taxi from my hotel and because it was the first day of Songkran there was virtually no traffic on the road. And maybe because of that, I managed to save quite a bit. It was 25 bahts for toll charges and another 175 bahts on the meter. Grand total of 200 bahts. And because it was reasonably cheap, I gave the taxi drive an extra 50 bahts as he was rather friendly and polite.
Somehow I got the feeling the tipping is no longer the norm in Bangkok as even a 20 bahts tip could get you very far with the person profusingly thanking you for it. I don’t know about other travellers but I do hope that if you have received good services (which I had on many occasion this trip) do tip them a little as their basic wages is actually quite low when compared with even Malaysia.

Have you ever tried hailing a taxi (those that have just dropped off passengers) from the departure hall?
You’ll save whatever surcharges there is - at least that’s what I’ve always done at the old Don Muang Airport
miss loi, i think with the new airport layout, it is not possible and the fact my friend got touted is an indication that it should not be done by first timer. Most taxis are scared of the fine which I think is set at 1,000 bahts. But I am sure for seasoned bangkok traveller like yourself, it might still be nice to save that extra 50 bahts