If you do need to collect bags then can just put in suitcase once you have them and check back in (assuming you would have checked luggage).
When you get off the first plane you enter the departure area at Changi. You then go through security at the gate to board for Samui.
Great airport, no stress at all.Edited: 07 June 2018, 06:03
It depends . . . are you in transit [ie don't clear immigration] at Singapore? Are you on one ticket.
Always found duty free prices at Singapore cheaper than Aus! BUT if you see a product buy it when you see it. Just make sure any liquids over 100ml are in sealed customs bag and don't break the seal!Edited: 07 June 2018, 10:06