Originally Posted by
blackmamba
They won't let you in the boarding area unless you have a boarding pass...
What are you talking about?
I have transited in TPE over 20 times and they have NEVER checked for a boarding pass in order to go upstairs.
As to leaving, in case anybody ever kept their eyes open their is a down escalator right next to the up one. They will not care in the least.
To the OP: I thought a diamond could use the lounge without an EVA ticket, but you could just read the EVA rules on this one.