Genotype =/= phenotype. SEA Chinese don’t need that much non-Chinese ancestry to look different from South China Han. Chinese Malaysians/Singaporeans and Taiwanese are good examples of this- genetically they’re basically indistinguishable but they collectively have enough non-Chinese ancestors (whether Malay/ISEA + South Asian or yuanzhumin + Euro) for different phenotypal traits to be introduced into the population.

For your “Japanese” looking relative’s group photo, the black top and red top women have a distinctly Siamese/Indianized MSEA nose shape that doesn’t exist among China Chinese.

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I only watched a little bit of the first 5-6 minutes of the interview. Didn’t catch where the interviewee said where she’s from, so I’m glad my instincts were correct on her being from thw South China Sea region but not a super Daic-shifted area (Guilin is SW Mandarin speaking so less SEA-shifted genetically than the Yue speaking areas). Still think she could pass in Jiangxi, Guangdong and probably Fujian although not as typical.

Mandarin Corner doesn’t look pan-Chinese to me because I don’t think she passes in the north. Maybe she could pass in the northwest but I’d ask throway.

I think a lot of dynamics in East Asia should not really be analyzed as "north" vs. "south", but rather through the lens of the following:
1) Emergence of agrarian cultures in upper Yellow River (led to Tibeto-Burmans/Sinitic millet farmers), lower Yellow River/Yangtze delta (led to proto/para-Austronesian millet/rice mixed farmers), west Liao river (initially millet farmers who ended up dispersed into pastoralism)
2) Rapid expansion of aforementioned cultures and interactions with local groups living in more "peripheral" areas

The whole "north" vs "south" thing in China can be summarized as a dynamic interaction between upper Yellow River descendants, lower Yellow River/Yangtze delta descendants, and the descendants of local southern hunter-gatherers/non-expansionist rice farmers

The Hebei schoolgirls don't have the Hmong-ish vibe Mandarin Corner has. Her laterally protruding cheekbones + vaguely SEA-ish nose and mouth make a difference. So do the larger eyes that occupy a larger portion of her face compared to the Hebei students, who all have proportionally smaller eye openings/sockets. She does vaguely resemble some of the Qin terracotta warriors but that specific face morph isn't common among modern-day N Han.

Agree that the interviewee looks vaguely NW Chinese in the gondola photo with her husband. 

Agreed, she can definitely pass in Northern China. As a former resident of Beijing with relatives from Hebei I can confirm that her type seems familiar.

I think her type is best described as a pan Eastern China phenotype, perhaps it was one of the core phenotypes of the Ancient Sinitic people.

I didn't watch the whole 5-6 minutes, only bits and pieces. I still think there's something about Mandarin Corner's nose/mouth/lower face region that looks off for Northern China- something about her nose bridge when viewed from the side just screams Guangdong/south of the Yangtze to me. Although you're right in that she can superficially pass in coastal Northern China.

Agreed with you. Btw I should have use the word "possible" instead of "probable" for any potential Siamese admixture. 

But I wonder if the some of the SEA vibes you detected in some SEA Chinese diaspora including me came from the Baiyue ancestry in Southern Chinese rather than recent SE Asian admixture? Considering how most Southern Chinese are a mix of Northern Han settlers and the indigenous tribes of that area. Btw does my younger brother look more northern-shifted than me and my sister?

I see. Can you elaborate on how the nose shape looks different from Chinese in China? Do you see any other southern traits in the group photo?

Btw regarding them looking "Japanese", it might be due to the fact that my relatives love Japan and try to emulate the fashion, thus making others think they look "Japanese". Or that they were mistaken as locals when traveling there, likely due to their fashion style.

I do noticed though that many mainland Chinese tourists in Thailand do look different phenotypically from Chinese Thais though even many of the Southern Chinese ones.

Most Chinese Thais are infatuated and interested about Japan and Korea, but very rarely feeling any bond or interest towards China, their ancestral homeland, sadly. I don't know why, but its probably due to Siamese/Thai government being pro-Japan and pro-West while being anti-communism for most of the 20th and 21st century and thus influencing the populace to think in that way. And the fact that Japanese and Korean culture and soft power is very influential in Thailand and many other SE Asian countries.

To me, its sad how most Chinese Thais have little interest and connection towards mainland China. For example, quite a long time ago, one of my cousins was talking about how he wants to learn Japanese because he thinks its cool and useful. I asked him if he is also wants to learn Mandarin, and he makes a rather bored unimpressed face and says he is not interested in it and don't see the point. I noticed this same apathetic and rather self hating attitude in many other younger Chinese Thais as well towards anything Chinese related which is unfortunate. I feel many are not even interested in Taiwan, HK, Singapore or any Chinese majority places unlike Japan, Korea and the West which they loved and admired. 

I think out of all the oversea Chinese descendants, Sino-Thais are the least Chinese culturally and linguistically and are probably regarded as foreigners by Chinese people. I feel even Chinese Americans or other Western Chinese diaspora are more "Chinese" than Sino-Thais. 

Apologies for the off topic, but I feel its very unfortunate. I think I'm one of the very few younger Chinese Thais who is interested in becoming fluent/proficient in Mandarin as my third language (would be nice if I can also learn Hainanese and Teochew) and learning more about my roots.