How do i book or purchase a flight ticket? Which flight ticket is cheap?

I use comparison websites and check different sites.

Scoot has promo

Go through websites like tripadvisor, expedia, klook. can get discounts or cashback too

Use an air ticket comaprison website like sky scanner to check ticket prices across various different websites. You can make the purchase by following the link in the comparison website. Which flight ticket is cheap is dependent on where you are flying to and what sort of ticket you are going for.