I just got back from a few nights in a suite at The Peninsula Bangkok.

Yes, she's a bit older and in need of a few upgrade's in the rooms to keep up with modern tech but overall the rooms are very comfy. The staff, grounds and pool are still beautiful.
I do like that It is slightly less pretentious than MO and I don't feel out of place wearing shorts and thongs (flip flops) from time to time!

I would still put it in the classic category along with MO Bangkok, albeit that MO is slightly more elevated overall.