The Thai nickname system isn't even that confusing because my country also has that (because of colonialism) but the nickname that some Thai people choose is just so funny too me 😭😭😭
Linguists like Weera Ostapirat have demonstrated that the core vocabulary word for "eat" links these two families via regular sound correspondences.
Proto Austronesian: *kaen (or *gaɲ / *kaeɲ)
Proto Malayo-Polynesian: *kaən (or *kan)
Proto Kra-Dai: *kan (or *kin / *kɯɲ)