Can South African vaccination certificates be recognized in Thailand for Singapore VTL entry?

Greetings oh wise tribe...I am a South African living in Singapore, desperate to see my South African parents. We've booked a week together in Thailand in March and have all the Thai passes approved already. I'm desperately trying to find info on whether it's possible for my parents to get their South African vaccination certificates recognized or authorized in Thailand, which would then allow them to enter Singapore on a VTL after 7 days spent in Thailand. The only vaccination certificates accepted to get on a VTL flight are vax certs from VTL countries. Praying someone has a lead 🙏