If you are a foreign visitor to Singapore, you must scan your thumbprints each time you arrive or depart the country. If you scan your thumbprints via BioScreen on arrival, you can use eIACS when you leave Singapore.
Your passport will not have a departure immigration endorsement and your embarkation card will not be collected when you depart using the automated lane. If you use a manned immigration counter, you will have to go through BioScreen clearance and will have your passport endorsed with a departure stamp.
Please click here to read more about eIACS.