I cannot stress strongly enough the need to respect the King. I know that, as an American, this seems a bit much, but it's true. You can be arrested for disrespecting him. Colleagues have learned this the hard way!!
Thailand’s Lese Majeste Laws
Disrespecting the King of Thailand or the royal family is a serious offense in Thailand; it’s officially illegal and strictly enforced.
People have been arrested for speaking negatively about the royal family. Even making jokes or criticizing the royal family on social media is illegal. Those convicted have received very lengthy prison sentences for doing so — tourists are not exempt.
Because all Thai currency features a portrait of the king, stepping on or damaging money is a serious offense — don’t do it!