Is there any simple ways to get thin fast?

If by "simple" you mean "uncomplicated" then yes. Eat less than you normally do and you will lose weight. If your metabolism drops as a result, eat even less. That's pretty simple.

If you mean "is there any easy way to get thin fast?" then no. Getting thin fast requires a great deal of effort, exercise and/or hunger, unless it is forced upon you like with illness or disease.