Overnight Singapore Itinerary
 

Hi I have never been in downtown Singapore and I plan to check it out for a couple hours but overnight. I arrive at 1130 PM on SQ and made a reservation at 330 AM for 6 hours as I will need to sleep at the Ambassador Transit Hotel T3. My question is for a first timer what I plan to do is go to Merlion Park and snap a few photos there then walk from there and check out some authentic Singapore Hawkers at Lau Pa Sat then go to Newton Circus before heading back to the airport for much needed rest before my next flight in late morning. How is this for the very limited time I have?

Let's review the facts:
You arrive 11:30pm. You then go to transit hotel airside to sleep for six hours at 3:30am. This put us at 9:30am.
Your flight leaves late morning; at what time? Even if it departs 11:59am IMHO you would not have time to enter S'pore, take the SMRT into town, immediately return and get process by immigration for departure and security.

I believe you misunderstood the OP's plans. He arrives at 2330. Then he wants to spend the next four hours going into the city, rambling around before returning to the airport for his Transit Hotel reservation at 0330. He then sleeps for six hours until 0930 ... and then catches his onward flight.

If that is the case, the plan won't work. You can only check in 3/4 hours before the flight and you need your BP and exit immigration to go airside to sleep at the transit hotel.

It depends. If it's a USA carrier, including for example SIN-NRT on DL, you can't get through passport control to airside until check in for your flight opens--even if you do OLCI and do not check a bag--until the check in for your flight opens, at most about three hours before your scheduled departure time.

However, if you are flying SQ (I've checked in the evening before for departures to the USA through FRA, so not nonstop), you can check in up to 48 hours before the flight, although the SQ FC check in lounge and special passport control closes in the middle of the night.

If I was wanting to do something like this, i'd be looking for a cheap room in downtown Singapore. Something like the Ibis Novena (which is v. close to Newton) springs to mind, and there's another Accor property on the airport side of town (the Grand Mercure Roxy) - pity as you've just missed their mega sale, which would probably make them cheaper than the transit hotel!

Also, I can't see the merits of going to both Lau Pau Sat and Newton, especially at that time of night. They're both open 24hrs but I always thought a lot of stalls closed up rather than going right through.

If you wanted a 2nd 24-hr experience then the Mustafa Centre is probably a good bet!

And you want to account for how you'd get from the City back to the airport at 3am (notwithstanding the possible issue with being able to check-in). The MRT will have stopped, you could I believe take a bus (1hr journey), or otherwise it's a taxi with a 50% surcharge for night hours tacked onto the bill.

I am starting off in HKG and transiting in SIN before going to DXB on SQ. So I will be checked in already and have my onward BP. How is Maxwell Road Centre? Isn't that the most famous or one worth checking out. I am going to take the 9 SGD Airport Hotel shuttle to the Fullerton since that is the closest Hotel to Merlion. Does this sound like now it could work?

Maxwell Road closes at 10pm I believe.

If you're on the 9.30am departure to Dubai then time will be of the essence, and I'd be getting a cab from the airport rather than waiting for the shuttle. Landing at 11.30pm you could be downtown by 12.15am all being well.

Quick photo of the Merlion then walk over to Lau Pau Sat for about 1.15am. Many stalls will be closed so by 2am you'll be done and be able to get in another cab to head back to the airport. Arrive there a 2.20am, through exit controls and to the transit hotel by 2.40am, into the room at 3am, some fitful sleep then an alarm for about 7.30am to give you time for a shower and down to the gate as boarding will start about 8.45am.

That doesn't sound like much fun to me.