how expensive is bangkok tourism？

Generally 4,000 yuan is fine.
If you travel to Thailand by yourself, three or four thousand is absolutely enough without being trapped and spending a large amount. Some Thais know that you are a Chinese tourist, and they will definitely hang people. After all, Chinese tourists have a reputation for being rich and silly. Be careful not to be fooled.
If you go with a group, in general, a regular tourist group will spend more than three or four thousand. In fact, there will be cheaper options if you follow a group, but cheap and informal groups are very risky. It is not recommended to choose the cheap type of tourist group in order to be cheap. After all, when you travel abroad, you still have to pay attention to safety.
Remember to keep the contact information of your local Chinese embassy.