André G. Haudricourt, in his seminal article De l'origine des tons en vietnamien (1954), showed masterly that the three tones of Ancient Vietnamese originated from ancient laryngeal finals. In short, sắc-năng tones derived from an ancient final glottal stop and hỏi-ngã tones from an ancient final spirant, while, by contrast, ngang-huyền tones developed in final vowel context. Haudricourt's model was developed and extended by James A. Matisoff (1973) to account for much of the tonogenesis phenomena in Southeast Asia. Gérard Diffloth (1989), contra Haudricourt, proposed to reconstruct an earlier Proto-AA creaky voice to account for Vietnamese sắc-năng tones, contrasting with a Proto-AA clear voice. This theory solves several tonogenesis problems within the VM group; on the other hand, it raises many new problems within the AA family. I this paper, I suggest that the Vietnamese tone contrast, sắc-năng vs ngang-huyền and its cognates in other VM languages, reflects an earlier tense vs lax contrast that results from the influence of the Chinese language during the Han times (206 B.C.--220 A.D.). In the end, this hypothesis reinforces Haudricourt's ideas.