For a foreigner working in Singapore, 'tax resident' status will be accorded if he/she works 183 days or more in Singapore (doesn't have to be 183 consecutive days). If this criterion is met, he/she will be taxed at Singapore's marginal tax rates.
If he/she has worked in Singapore for more than 60 days but less than 183 days, taxation will be 15% or resident tax rates, whichever is higher.
If he/she has worked in Singapore less than 60 days, he/she is tax-exempted (Ref. to IRAS website).
However, please note that Singaporean citizens are tax-residents by default.
