Next month I'll be flying from AKL to HKG via SIN and have got a 13 hour stopover. I arrive at about 19.30 and have booked accommodation at the Ambassador Transit Hotel. After checking in and leaving my overnight bag in the room, I'd like to clear Immigration & Customs and spend a couple of hours sightseeing.
I believe that sightseeing trips are laid on for transit passengers, but I can't imagine them being that late in the evening. Any suggestions would be most helpful.
Also, if I do leave the airport, and as I'll be relying on public transport, when is the latest I can to get back to the Transit Hotel?

Many thanks.