Not really a visa question as I know Thai national has 30days exemption to go to hong kong. As you lot knowledgable my question is what is required for me and wife to take Niece and Nephew to Hong Kong without their parents? Also do children in Thailand have individual passports like in UK or on their parents?
TLDR : Answer Summary
To take your niece and nephew to Hong Kong without their parents, you will need written consent from both parents, typically in the form of a notarized permission letter. Some commenters suggest obtaining this document from the amphur along with the children's birth certificates to ensure legal compliance. Additionally, it's implied that the children's ages (4 and 8) are important, and while traveling with you as their legal guardian should pose no issue, it's advisable to check with your airline for any specific regulations they might have regarding traveling with minors.