u seem like a very dedicated 18 yr old singaporean ...
ur plans look good, but if it were up to me i wud start flying ASAP without the hassle of collecting degree after degree before stepping into flying.
but in singapore, u kinda have limited but good options. SIA is great to work for but then they have age restrictions for u fellas.
but it wud still be great to get an Airline job at 26 yrs old. pilots out here in the "western" world would die to get that. i have friends who at 35+ havent yet made it to airlines, but also some who are Captains on the 737 NGs with 5000+ hrs on type, and are only 25 yrs old !
anyway u can decide for urself, we can just share info !
cheers,
FT