PRC have extended the 96/144 hr scheme for many nations inc most Western and Thais
see details here
China 240-Hour Visa Free Transit Policy 2025
China Transit Without Visa (TWOV) | Visa Free Transit Rules
It;s not all smoky cites in fact te very best valleys are only 200 miles North of me in Xishaungbanna prefecture where local Dai/Thai plus similar hill tribes have lived for aeons.
Dali and Lijiang no whave airports I wa slucky to vist them in the last century pre mass tourism in the foothills of the Himalayas very nice.
With trains to Laos could make a nice triangle fly in explore Lake Dian and many interesting things in Yunnan then head to what Thais call Sipsongpanna (12 rice valleys) where life similar to rural C rai but with a red tint.
Bon Voyage, my ex Chango cop fried assures me the passenger boats from C Saen to mengla are off since that shooting c2013 but for the adventurous it is legal WITH A VISA to hitch a ride on a ric ebarge passing between Burmaand Laos to teh first port in Thailand , probably far easier going South if holding Thai Visa already, or be sure to find C Saen Immigration, my fairly strict but friendly littel Office,
I have re entyr but as you cannot predict arrival time de to currents If it was me I'd forewarn Immi and try not arrive after 3pm Friday .
Ver few westerners using the route as even my ltd Mandarin wasn't much help with the Captain however kids spoke enough Engrish to recognise a punter, Downstream c 11 hrs in daylight only so likely arrive 5pm