The airline's internal booking system seems to have failed here which sucks for the OP BUT the airline's own website tells people to verify their eligibility to transit and enter a country via the IATA website https://www.hongkongairlines.com/en_...el/visas_taxes which when I completed that as a Thai citizen it did correctly state visas are required.

A traveler is responsible for their own visa documentation even though the airline failed here. Since their internal system failed they should acknowledge this and offer a credit as a customer service gesture but a refund is not due here in my opinion.