Thanks to you both for the lesson, but I was going to Mai Khao, not Patong (sorry about not clarifying that initially).
5 additional km is one third of the total, and definitely not the quickest route around midnight (there was no trafic whatsoever).
I know a scam when I see one and have seen far too many in Thai taxis.
I know I should let it go / not let it ruin my vacations (it doesn't) / it's just a couple dollars/euros, but I just don't like it and wanted to inform others that it does happen a lot in Phuket, even with the new metered taxis.
I also not sure about the THB amount per km (I am willing to give him benefit of the doubt for that one).
Our meter was showing 326THB for 20km, which is much more than the prices mentioned in the article below (although that information may be outdated since it is 6 months old, or there might be a night surcharge of some kind) :
http://www.thephuketnews.com/phuket-...cess-48508.php
Current fares are: B50 for the first two kilometers; then the fare per kilometer is B7 up to 21km, and B6 a kilometer after that.
Fares can be expected to go up. “A higher tariff is now being considering by the NCPO. A decision is and expected to be announce by the end of this month,” Phuket Land Transportation Office (PLTO) Chief Teerayut Prasertphol told The Phuket News.
If agreed by the NCPO, that fare will be B50 baht for first 2km, then B12/km up to 15km and B10/km after that.