I wanted to try the Zenfone Max Pro M1 too (Stock android + 5000mah battery + 3 trays slot) but it take ages to launch in SG.
I was also comparing between the 2 before I got the RMN5.
The specs are so similar that you have to pick at the bones to choose either.
The size of the Asus is slightly larger and thicker compared with RMN5, but it comes with a 1000mAh battery, which translate theoretically to a 20% increase of batt life. It also has a dedicated dual sim + SD card slot.
RMN5 on the other hand, has a camera with larger aperture (Good if you take more photos indoors or at night), has a IR port for remote control. It is also rather slim, which may seem easier to slip.
I have yet to use an ASUS phone, so not sure how good is the software support, but so far XM is pretty quick with their updates.
ASUS MY is selling the Max Pro M1 3/32 version at 599RM via Lazada now. Someone also posted that JTBC was selling the export RMN5 3/32 at S$195. Really close fight at these prices.