Taxi fare

It should be 450-500 baht and that includes 50 baht airport surcharge and 70 baht highway tolls.  Cost and travel time can change due to amount of traffic and time of day.

If traveling light you might consider the train because hotel you mention has walkway connecting to Surasak BTS station.  You would take airport train to Phaya BTS station then take Sukhumvit line train to Siam BTS station and then catch train on Silom line to Surasak BTS staion.  Trains are frequent but after midnight forget taking a train and go by taxi.

Have you been to BKK before? Do you know your way around?

Looking at the map, it looks like this hotel is right next to Surasek BTS. I would take the all stations Airport Rail Link to Praya Thai, then jump on the BTS at Praya Thai. You would need to get off at Siam to change trains to go to Surasek BTS (just go up/down escallator at Siam). Cheaper and probably get you there quicker than getting stuck in traffic. The only thing is the BTS will be very busy if you are going peak hours but so will the roads.

I almost agree. Price is a little on the high side, maybe 400 thb and I've never paid that airport surcharge. All the taxis start with 35 thb on the clock. Also they don't charge by time, just by distance. You do have to pay the tolls though. I've tried the train. Its a pain if you have heavy luggage. Just take the lift to the top floor, throw your luggage in the taxi boot and sit back.