UA Mileage Plus RDM Bonuses apply to flights operated by United, TED, United Express, US Airways, and LH (officially only for trans-atlantic flights, but some folks have gotten them for trans-Africa runs, as well). No other Star Alliance partner airline grants them for flights operated by them (even if codeshared with UA).

SK does have a premium Economy cabin, but it is available only to full-fare Y, I believe (it is not automatically granted via Star Alliance status, like E+).