I guess Indonesia requires a "Wali"/guardian (father, older brother,..) because the name of the Wali is stated in the Indonesian KUA's Marriage Book .
What will happen if in the specific Hong Kong's mosque where they marry , a Wali is not required ?
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From
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3067457
Title : Marrying Without the Consent of the Wali (a Case Study of Pakistan) Compatibility of Pakistani Family Laws with UDHR
By Asmat Ali Khan , Nov 2017
... The Shafi’i, Maliki and Hanbali schools say that nikah entered into by a woman herself, without the permission of her wali, is invalid and void. However, the Hanafi ruling on the said matter is that a woman can enter into a marital contract by herself without the permission from her wali ...