There is a difference between Asia Miles (AM) and Marco Polo Club (MPC). AM gets you miles to redeem, and MPC gets you status within CX and OW. See Section 9.1 in:
http://www.flyertalk.com/forum/catha...-about-cx.html
18K in J can get you 22.5K Club Miles. You are still short of the 30K required for MPC Silver.

If you fly J, you can get 1.5X EQP if you join AA. With 18K BIS miles, you can get enough EQP to get to AA Gold, which is rather useless.