汉语“是”借入台语不早于晚唐,,台语里的分布表明它是在台语分化为三个分支以后,西南支进一步分化以前。本文不同意把tchai^3看作台语共同词的观点。
There are two "to be" words in Thai language. Except pen^2 from a Thai verb, tchai^3 is a loanword from Chinese. The loanword shows some phonetic and syntactic characters of Chinese in history. It was loaned into Tai in Tang Dynasty.