O3 (M122) distributed throughout Central Asia, East Asia, Southeast Asia, and the Austronesian regions of Oceania, with 03a3 (LINE1, M159) represented in Hmong-Mien people; and 03a5 (M134) in Sino-Tibetan peoples.
On the basis of this classification of Haplogroup O genetic markers, the National Geographic project has completed tracing for a number of racial groups, although no analysis has been done on the subgroup Hmong-Mien who carries genetic marker M159.
In a separate research project that focused specifically on Hmong-Mien 'Imt DNA genetic/molecular variance", Bo Wien (2005: 725-734) and 17 other university scientists in China (Shanghai and Yunnan) and the United States (Cincinnati, Ohio), took blood samples from 537 individuals in 17 sites in Hunan, Yunnan, Guangxi and Guangdong provinces, China.
A close "relatedness" between the Hmong-Mien (H-M) people and other southern East Asians (SEAs), with the Miao in Hunan (believed to be the site of their original home) "closer to" northeast Asians than other H-M populations (p.
Ala general southern origin of maternal lineages" with "more contact" between Hmong-Mien and northern East Asians than other people, due to "the higher frequency of north-dominating lineages observed in the Hmong people" (p.
Previously, Hmong-Mien (H-M) languages were included in the Sino-Tibetan language family, but are now seen as being a family of their own.
In my view and from all the accessible evidence, an origin in China is the most plausible, especially given the results of recent DNA testing on the distribution of genetic markers which clearly show a southern China origin for the Hmong-Mien people.