Regarding the application process, there is nothing particularly noteworthy to mention. Simply follow the instructions on the webpage below and submit your application by filling out the form. You will need to upload a copy of your Hong Kong/Macau passport or Chinese passport, your mainland China operating license, and a photo of your mainland China radio license (minors must also upload copies of their guardian's travel documents). Once the application is received, OFCA will contact you via email.
https://eform.cefs.gov.hk/form/oca009/sc/
If you do not have an HK ID, the callsigns on ATO and ASL are VR2/BY; if you do have an HK ID, you can directly use the VR2 callsign.
An ATO is equivalent to an inland operating license. Once obtained, it allows you to operate in Hong Kong, with a validity period of 5 years. The application fee is HKD 150. If you only hold an ATO, you can only use equipment that has already been registered by others in Hong Kong. To operate independently, you need to apply for an ASL, which has a validity period of 1 year and an application fee of HKD 160.
However, I don't recommend bringing your own equipment to Hong Kong for operation, as doing so strictly according to Hong Kong law would require a one-time import and export license for each of Ham's daily use radio receivers in order to legally bring them into and out of Hong Kong. The combined application fees for the two licenses amount to 300 HKD, and they can only be used once. In addition, there are also application fees for ATO and ASL if it is your first time.
Currently, from my personal experience, the most troublesome aspect of applying for a Hong Kong license is paying the fees. Based on my experience last year, OFCA only supports three payment methods: cash, postal check, and PPS online payment. The only method that allows online payment, PPS online payment, requires users to first register with a Hong Kong bank card at a payment machine in Hong Kong before use. For people outside the Greater Bay Area, it is really difficult to pay these fees.