You are a tax resident for a particular Year of Assessment if you are a:

Singapore Citizen or Singapore Permanent Resident (SPR) who normally resides in Singapore except for temporary absences;

多久算temp不知道，但是如果你有固定房产的话“暂时离开“的理由说的通。我有个朋友去美国多年，组屋租金都是按本地居民交段的。