Depends upon your Nationality, can either be 30 or 90 days. The counting of the day started from the first day you step there (with the first full day being the day you step in). The countdown stops when you leave Singapore, and it resets for another 30 or 90 days once you again enter Singapore. This stay period doesn’t affect how many times you visit. For every tour there’s always 30/90 days are permitted.