Bangkok is now famous because almost all tourists suffer scams, and because of them you can loose a lot of money, miss the most impressive attractions and have a very bad time in a place where you want to feel just the opposite.
The palace, temple, etc. (any attraction) is closed because “today is a holiday in Thailand”
This is the most typical scam when you take a taxi or a tuk tuk (or even someone approach you in a friendly way in the street with “a newspaper under his arm”). Don’t trust them, there are tons of tourists that have missed the Royal Palace or some of the most impressive temples just because their taxi drivers wanted to take them to a shop or didn’t want to drive them to that place. If they tell you that, get off the taxi/tuk-tuk, he will cheat you for sure!
“It will cost you $900 BHT to get to X place in my Taxi or Tuk-Tuk”
NEVER NEVER take a Tuk-Tuk, they don’t have any system to measure the legal fare to charge you, so they will overcharge you for sure, specially those waiting for naive tourists in Khao San Road or any tourist street. If you don’t want to take the boat to move through Bangkok from one of the peers (the cheapest and safest way to move around), take a Taxi in one of the streets or avenues that are around but look like local areas, so you can flag down a honest taxi driver. Once you take the taxi, ask for the METER so they will have to use this device in order to charge you and they won’t be able to cheat you that easy. If they refuse to take you with the Meter, just get off from that taxi and ask to a second one and so on, we can tell you for sure that you will find a honest one and that at the end you will pay a fair price.