我在iras上面看见一条说: Foreigner who has stayed / worked in Singapore (excludes director of a company) for 183 days or more in the previous year. i.e. the year before the YA. 如果不满足这条会被当做Non-resident收税。
而Non-resident好像最少要交15%的税: Taxes on Employment Income The employment income of non-residents is taxed at flat rate of 15% or the progressive resident tax rates (see table above), whichever is a higher tax amount.