Check in opens at 0430. I would suggest reserving a room at the terminal 1 Transit Hotel. Rooms are rented in six hour blocks at about $38 US or $55 Singapore. Reservations are required.
[email protected] for internet reservations. I have used the hotel on my "Singapore mileage runs. DO NOT clear customs. The hotel is in the "secure äreä of the terminal. Just follow the signs. It is about a 8 min walk.
The SATS lounge is a nice quiet place to wait after 0430 check in. You will be given an invitation with Gold card or business class ticket. Check in takes a bit longer now because all hand carried bags are opened and checked with an ion detector, Then x-rayed as before. I would be at the gate for check in at 0545. "Last trip was 16-18 Feb, so information is fairly current.