I am trying to find a school to study Mandarin Chinese anywhere in Thailand. As I have studied in Chinese I am not a beginner. Can anyone offer a suggestion? Thanks very much. Peter

Confucius Centers can be found at many major universities. They are funded by the Chinese government, have resident native Chinese teachers, and administer the HSK Chinese language proficiency exam. 

An alternative in Bangkok is the Chinese Language Center. This is funded by the Taiwanese government and not only teaches Chinese as a foreign language but also to native standard (in my day most of the native-level students were children of Taiwanese businessmen). 

The main difference is that with the Confucius Center you will learn simplified Chinese and at the CLC you will learn traditional Chinese, just like they do in Taiwan. I'm told that even "simplified" Chinese gives people in China a major headache, but many people I've spoken to say that you will eventually develop an edge if you learn traditional Chinese if - IF - you stick with it for long enough. 

Another thing is that once you get past the basics the Confucius Center starts to load the curriculum with Chinese state propaganda. I don't know if the CLC do same with Taiwanese perspective, but it wouldn't bother me either way because I'm quite happy to hold my nose over the content during a language exam, given the heavily subsidised cost.