Why can't Thai clothes wear gold?

Yes, but ordinary people can't wear it.

Because of the unstable political situation in Thailand, it is best not to wear red, yellow and pink clothes (because red shirts and pink shirts are so impressive).

If you go to a temple, you'd better wear some light-colored clothes or black ones. Ladies should wear long trousers (shorts are not allowed), not too exposed, and shoes should be simple, because they have to take off their shoes when they go in.