Weird that this is downvoted; it is quite factual.
I think you're right about it being centered on Zomia:
> The majority of identified targets were located in northern Myanmar.
but your specific example of the illicit trade is slightly off: aiui, the relevance of the golden triangle as an opioid producer has actually fallen off since the early 2000s as a result of DEA pressure and market shifts, but the slack was taken up by amphetamines (mostly ya ba).
https://www.unodc.org/roseap//en/2021/02/myanmar-opium-surve...
> A new report from the United Nations Office on Drugs and Crime (UNODC) confirms that production and demand for opium has further declined as the region’s synthetic drug market continues to expand and diversify.
That change in drug profile appears to also be true in Yunnan: https://www.frontiersin.org/articles/10.3389/fpsyt.2018.0025...
> The prevalence rate of heroin use decreased from 0.67% (0.63–0.73%) in 2011 to 0.57% (0.53–0.61%) in 2015, while the prevalence rate of methamphetamine use doubled from 0.20% (0.17–0.24%) in 2011 to 0.48% (0.46–0.50%) in 2015.
However, you are absolutely correct that even accounting for trends, Burma is the source of most of both opioids and amphetamines: https://www.brookings.edu/wp-content/uploads/2016/07/a-peopl...
> Myanmar is believed to be the single largest supplier of China’s drug market. In 2013, 92.2 percent of the heroin and 95.2 percent of methamphetamine seized in China were traced to Myanmar.
All that said, Chinese in northern Burma also tend to be associated with other rackets:
> Solely in Wanding (畹町), a river port bordering Myanmar in Ruili city,Yunnan province, over 960 suspects of telecom fraud and over 100 suspects of cross-border gambling
Cross-border gambling is huge. https://en.wikipedia.org/wiki/Mong_La is basically a city-sized casino, built directly across the border from Yunnan (which is incredibly porous due to the terrain, so just clamping down on crossings doesn't work). https://en.wikipedia.org/wiki/Pangkham is the same deal but in Wa territory, not Shan.
The CCP really really hates cross-border gambling for a variety of reasons, including capital outflows and its nexus with domestic corruption:
https://agbrief.com/news/china/09/04/2021/chinas-cross-borde...
https://www.asgam.com/index.php/2022/02/17/china-vows-to-acc...
There's also a lot of jade/amber/wildlife smuggling but the gambling thing really is astonishingly huge business in northern Burma. So, I see it as a "yes, and": there's a lot of reasons why the CCP would want to crack down on the behavior of Chinese in northern Burma, and the drug trade is a plausible one.