There are a few different interconnected terminals there using trains. You may have to pass through another security screening, which can be variable depending on how many people are there. As one data point, when I was there a couple weeks ago it took me about 15 minutes to get throughs security and another 15-20 minutes to transit from one concourse to another.

Some pictures of the Club ANA lounge (the only open lounge in the whole airport... keep in mind the SQ and Thai lounges have restricted hours):

http://www.flickr.com/photos/nakedsky/sets/