Does it need quarantine to fly from Bangkok to Hong Kong for transit entry? What is the approximate cost?

The transit entry from Bangkok to Hong Kong requires quarantine for 7 days. From August 12, 2022, all personnel arriving in Hong Kong from overseas must immediately register and confirm the information at the arrival sampling station in Terminal 1, and conduct nucleic acid detection and rapid antigen detection and sampling on the spot. Generally speaking, the cost is only more than 10,000 RMB (except for mainland quarantine). According to the query data, only one nucleic acid test is needed to fly to Hong Kong, and the green code of the embassy is not needed. The air ticket from Bangkok to Hong Kong is only over 2,000 RMB, and the air ticket from Hong Kong to Shanghai is less than 3,000 RMB, and my friend has successfully booked a very cheap isolation hotel in Hong Kong. In general, the cost is more than 10,000 RMB (except for mainland isolation).