Credit to Flynous OP :-)
Realized my error on the missing links now thanks, didn't see it was a multi city listing :) Not sure why it was showing a different price before as clicked same link, all good now tho and seems like a great deal.
I think if you try and buy the one-way AMS-DPS it is £400. But buying it as a multi trip is cheaper. All three SIngapore flights are on the same link.
Was viewing in incognito mode, although skyscanner claim they don't slowly increase their prices anyway. I see £299 now so no idea.