Also received a $false - BOOK.
Screenshot: http://imgur.com/a/SGSQu
Screenshot: http://imgur.com/a/SGSQu
berlin,3 days
boston, 3 days
shanghai, 3 days
I've booked marked it. Cool site.
It seemed to me that it couldn't find a route from London to Khon Kaen (Khon Kaen isn't an international airport), but interpreted that as a zero cost flight. The route it gave me was Gatwick -> Khon Kaen -> Bangkok -> Singapore and the cost for the whole thing was a fraction of what it should have been.
The way to make that route work, by the way, is to go Gatwick -> Bangkok -> Khon Kaen -> Bangkok -> Singapore (or throw Chiang Mai or Hat Yai into the mix). You can only reach Khon Kaen by air through internal flights in Thailand.
Interestingly enough I just booked this trip two days ago directly through the airlines (Air Canada and Delta).