Upvote:9
According to Lufthansa twitter, an LH N fare marketed by LH and operated by SQ maps to an SQ P fare class and earns 150%.
I couldn't find an up to date booking class alignment table for star alliance. There is an old one here but it doesn't have premium economy on SQ. SQ has T, S and P premium economy fare classes and all earn 150% on M&M according to wheretocredit.