and also the most critical qn is go to airport at night or Grab?? in the middle of the night? given such an early departure flight gosh...
Go 2 - 2 1/2hr before your flight. No need to go the night before and camp at airport.
for the insurance, i will buy next weekend b4 i go.
If there is a discount now (always have), then just get it. don't have to wait actually. But up to you.
Lunch at Pratunam market?
personally, i don't think need to plan dinner and lunch eat at where, unless there is a specific place you want to go to eat. otherwise, just eat wherever u are at the point of time.
central world, Pratunam is only side by side. now with the bridge, it's even easier to walk.
no need to split into two days. if you been to orchard, tampines mall, you been to central world.
massage can also be anywhere, can places even offer hotel room massage service. you can check with Arunda if u want, since they basically just beside your hotel.
u can leave your luggage at your hotel after you check out. u still have around 1 - 1 1/2hr to walk around before u leave for airport.
your night activity too little. massage then go back hotel? and massage after dinner? maybe massage before dinner? are you those type that sleeps at 9-10pm oversea or in sg? otherwise, all your night, you can go to night market or pubs instead of dinner > hotel.
u are basically wasting all your nights there as far as i can see.
lastly, if possible, don't buy last min item at their airport. markup x 3-5.
if you need to burn your cash before you come back, i am willing to collect that cash u want to burn at your house. get your item over the days when you at the city, not at the airport.