Hello, I am now in Thailand, holding a tourist visa, and I just passed the interview of the company, so I need to apply for a work visa. Can I only go back to China with an invitation?

No, according to personal experience, generally speaking, it is ok to go back to China with an invitation letter and various documents, or you can go to a third country to handle it. Like going to Malaysia or Laos. Take Malaysia as an example. You can apply for a tourist visa to Malaysia at the nearest Malaysian embassy or consulate (round-trip air tickets and hotel accommodation vouchers may also be required) and at the Thai embassy or consulate in Kuala Lumpur or Penang, and then apply for a non-B visa with the invitation letter and various documents given to you by the company. If the procedures are complete, it usually takes only one working day. Then go back to Thailand. Other countries and so on. I don't know about the intermediary, but generally speaking, the cost will not be very high, because this is a very common situation. You can find a Thai friend or a Thai travel agency and see if it can be done through an intermediary. In addition, there is a saying that I have only heard of it, but I have not verified it, that is, tourist visas can be converted to non-B at the General Immigration Bureau in Bangkok, but the required documents are very complicated, so it is not as convenient as going to a third country.