he put the nags into the trunk before I had a chance to mention the meter before getting in

Again, rule #1 should be "never enter a taxi without first negotiating the use of the meter, or a mutually-agreed upon flat-fare, and any specific routing preferences."

Although this may be preceded by, "never take a standing taxi", unless it's stopped in traffic, with the engine running, and the red availability light is illuminated.

You may be better off using GrabTaxi, but that does mean you pay an extra 25 baht. But, there are a ton of promotions.