Anyone below 2 years of age requires an infant ticket. Infant ticket is 10% of full IATA fare.
Ie, full fare SIN-BKK $848. Most people buy at promo fare, say $250 for adult. Infant pays 10% of full IATA fare. Full IATA fare usually means that yhe ticket is the most flexible and endorsable, mesning you can (change) travel on any airline. The promo fares that we usually purchase are valid on the airline/carrier we purchase ftom.
Budget airlines charge differently. Tiger charges $50 per sector.