His 'previous' mortal body and cultivation base weren't really from his past life, but they have always been hiding in his Yuan Shen, within the Six Paths Reincarnation.
Although his 'previous' strength was not very powerful in his eyes now, they were still several times stronger than the Qi Practitioners that opened the pseudo-Six Paths like Ma Sansou, and was even on par with the likes of Qing Feng.
If he could recover his 'previous' cultivation base and arcane energy, and successfully integrate it into his current cultivation base, then his strength would see a quantum leap!
Even though it would not make him twice as strong, he would be at least 30% to 40% stronger.