China on balance is more expensive than SE Asia but not Japan or Korea levels. While you can find frugal alternatives for accommodation and food, even in the most expensive cities such as Shanghai and Beijing, intercity transportation will cost more due to cost structure and distance, as will admission to sights. In the low-budget travel department, it is nowhere close to Europe. Excluding hotels and sights (which are completely depending on your itinerary that we don't know), take your Thailand experience and increase daily expenses by 20% for budgeting purposes.