Take the total package of your current salary in SGD and add 50% on top converted to RMB. This kind of hap hazard recruitment is definitely not expat and confirm local hire, which is a wild wild west market.

Anything <50% will all get eaten up by tax, relocation costs, home trip costs, forex fluctuation and additional spendings. Also make sure they house you in an upmarket condo, do not leave it to them vaguely like "company provided". Otherwise they will dump you in some crap neighbourhood sure die jilat jialat.