You have describe exactly what I have. I had sever acne then when they were gone, I was left with brown spots and I'm also Asian (very fair normally to olive when I tan). I have founded products that contain:
HYDROQUINONE 2% or SALICYLIC ACID do the trick nicely.
Have you tired John Plunkett Superfade, it contains both SALICYLIC ACID 2% HYDROQUINONE? And sometime else called PADIMATE, which means you can use this product during the day under sunscreen. 2% HYDROQUINONE is the strongest dose you can get over the counter here in Australia, you also have to stay out of the sun but. It can also fade freckles though freckles take more time than brown spots from acne.
This over a period of 3-6 months has disappeared all my spots that people actually compliment me on my skin. Which to me is huge, especial since I've been pimple prone for most of my adult life! Hope this helps!