According to the Chinese newspaper People's Daily, Shanghai has signed the twinning with the city of Chiang Mai, however the twinning was signed by Pravit Sihsobhon, the governor of the province. If the twinning is with the city, one would expect the city mayor to sign the agreement. For the twinning with Yogyakarta, the report of Chiang Mai Mail confirms it's the province with is twinned with the Indonesian province. A list of official friendships between China and Thailand only adds the province for Chiang Rai, for the other ones it is not clear if its the town or the province.
- Beijing - Bangkok
- Shanghai - Chiang Mai
- Yuannan - Chiang Rai Province
- Henan Province - Chon Bury
- Kunming - Chiang Mai,
- Yantai - Phuket
- Nanning - Khon Kaen
But can someone maybe supply me with a complete lists of friendships and twinnings between Thai entities and those of other countries? I could not find any in English yet, and one in Thai would not fall the confusion between town and province. I'd be especially curious if there'd be any such relationships between Thailand and Germany, with Google I failed to find any.