Hong Kong to Bangkok to Busan

You need one for Hong Kong, but I'm not sure whether you need it for Thailand also. To apply for the HK entry permit, you can go to the embassy or get contact with the Hong Kong Immigration Department and send the required documents by post: the application form (ID 1003A), your recent photo affixed on page 1 of the application form, photocopy of your passport, photocopy of your financial standing proof (bank statements, saving accounts passbooks, tax receipts, etc.) and employment proof (if any) (e.g. salary slip), and photocopy of your transportation arrangement proof.