Income tax rates depend on an individual's tax residency status. You will be treated as a tax resident for a particular Year of Assessment (YA) if you are a:
Singapore Citizen (SC) or Singapore Permanent Resident (SPR) who resides in Singapore except for temporary absences; or
Foreigner who has stayed / worked in Singapore (excludes director of a company) for 183 days or more in the year preceding the YA.
Otherwise, you will be treated as a non-resident of Singapore for tax purposes.