It depends on the reason for spending the weekend outside of Singapore. Your Singapore employer must certify that that weekend spent outside of Singapore was meant for business purposes. For example, assume that you have to travel to a subsidiary in China for a series of meetings. You leave Singapore on Thursday afternoon and have a full schedule of meetings everyday except Sunday. You return to Singapore the next week on a Tuesday afternoon. You would have spent 5 days outside of Singapore (i.e. Thursday, Friday, Saturday, Sunday and Monday). Tuesday is considered as a day spent in Singapore. This is provided you elect for the alternative method of computing days spent outside of Singapore.