The price of a round trip flight from Toronto to Thailand depends on several factors such as departure time, airline, booking time, etc. Typically, a one-way ticket can cost between \(800 and \)1,500. A round-trip ticket from Thailand to Hong Kong can cost between \(500 and \)1,000. The cost of staying in Hong Kong for 5 days depends on personal expenses such as accommodation, meals and activities, which ranges from US\(1,000 to US\)2,000. The price of a flight from Hong Kong back to the mainland is similar to that from Toronto to Thailand, probably between \(800 and \)1,500.

Please note that the above prices are for reference only and actual prices may vary. It is recommended that you plan your trip in advance and check specific flights and prices.