The reason why Singpost normal mail can take up to 3 weeks+ is because:
1) Singpost prioritises AM mail, letter mail and registered mail
2) There is a limited number of delivery personnel in the area, so if there are many letters, AM/registered mail, parcels will be held back until all the other mail are fully delivered. Please understand that by choosing the cheapest form of postage, it would mean slow delivery and possible lost/stolen mail.
Should you wish for safe and fast delivery, please choose Qxpress courier.