From the Financial year - i.e. Jan - Dec for Singapore.

Out of 365 days, you should have spent 180 days (for Singapore) in the country, to be eligible for tax. If you say, spend every weekend in Malaysia - which is just a short drive away, and add in the regular duty travel, and add some days for vacation etc. at the end of the Calender year, IRAS (Inland Revenue Authority of Singapore) will count days in country vs days outside the country.

Same goes for Australia if I am not mistaken.

For example, Between Jan 1st to December 31st. You spend Jan - to March in Singapore, next three overseas, and vice versa .. does not matter.

As for less than 365 days, Singapore has some ruling - if you start residency in Singapore for less than 180 days of the calender, eg: start in July, then they have a fixed taxation, and less than 60 days (eg: start residency in November) then tax-free.

Look up the IRAS site for Singapore. Same goes for Malaysia, and other regional neighbours