Don't know if it's common knowledge but there's a new taxi app called inDriver that's worth trying out. It's exactly the same sort of thing as Grab Taxi but much cheaper and they have way more cars when I compare the vehicle location maps of both apps (in Pattaya at least and they're probably all Grab ship-jumpers, no idea about the rest of Thailand). So just like Grab you enter where you are - or the GPS in your phone does it for you - then you enter where you want to go and it comes up with a recommended fare, adjustable which you can accept or lower to see if any drivers will take that offer. Then there's an add 10 Baht button if nobody does till someone accepts, but I haven't tried this auction-styled method and have just used the recommended fare which is about 50% cheaper than Grab for the 2 trips I've used them for now.
Handy to know for those of us who no longer drink drive, and like the idea of half priced taxis