Shin opened with a stunning nine-under-par 62 on the River Course on Thursday and had another solid, if less spectacular, round on Friday.
The 24-year-old picked up four birdies before bogeying the par-four 16th to put herself 12 under through 36 holes.
Danielle Kang was her nearest challenger at the midway point after signing for a sparkling 64 in her second round.
The American teenager started badly with a bogey at the par-five third, but recovered superbly to charge up the leaderboard. She collected eight birdies - including six over the final eight holes - and did not drop another shot.
Holland's Dewi Claire Schreefel (66) and American Paula Creamer (67) were tied for third on 10 under.