If you can get a good rate at the IC then that would be perfect. Right down the road from Siam Square, right on the skytrain so easy to get around.

However, to get to Siam Square from the Conrad is just 10 minutes or so. Plan on < 2 minutes for a tuk tuk or taxi or conrad shuttle to get you to the Skytrain stop and another 5-8 min for the Skytrain to drop you at Siam Square. It's really easy.