What should I do if the driver claims the attraction is closed?

Ignore them. This is a common ruse to take you to a gem shop or tailor where they receive a commission. Politely tell them you still want to go to your original destination.

Is it rude to decline a taxi?

Not at all. You are a customer. If the terms are not agreed upon, you have every right to decline and walk away.

How to avoid taxi scams in Bangkok

Always insist that the driver turns on the meter before the car moves. If they refuse or suggest a flat fee, exit the vehicle immediately and hail the next one.

Use a Ride-Hailing App. Download Grab or Bolt. These apps provide fixed prices upfront and track your route, eliminating the need to negotiate or worry about the meter.
The 'Meter Only' Rule. If you hail a taxi on the street, ask 'Meter?' before getting in. If they say 'No' or give a high price, do not argue; just close the door and wait for the next one.
Check the Meter Reset. Once inside, ensure the meter starts at 35 THB. If the meter is already running or the driver refuses to turn it on, insist they do so or leave.
Navigate with GPS. Keep Google Maps open during your ride. If the driver takes a route that deviates significantly from the app's suggestion, kindly point it out to let them know you are watching.

What should I do if the driver claims the attraction is closed?: Ignore them. This is a common ruse to take you to a gem shop or tailor where they receive a commission. Politely tell them you still want to go to your original destination.
Is it rude to decline a taxi?: Not at all. You are a customer. If the terms are not agreed upon, you have every right to decline and walk away.