The Asian range strategy trades the quiet hours themselves, buying at the bottom of the overnight range and selling at the top, on the theory that the market stays inside it until London opens.
The claim is that the Asian session is a predictable range that can be faded.
We tested Asian-session range fades across 17 years of data with real trading costs, and found no edge. The range was quiet, but it was also narrow, and after the spread at those hours the small moves inside it left nothing. When the range broke early, the fade lost more than the successful fades had made.
The reason is arithmetic: a strategy whose winners are a few pips inside a quiet range is a strategy whose winners are about the size of its costs.
If you trade it anyway, compare the average winning trade with the spread at 2am, and do not use a backtest that assumed the London spread.