Hello:

I am an American, currently visiting Chiang Mai. I've been invited to volunteer with an NGO in China starting next month for a period of two months. I will need to travel outside of China three times during my two month stay (once to London, once to Seoul, and once to Vietnam). I have three questions: First, what type of visa do I require? Second, can I obtain my visa in Chiang Mai or, if not, Bangkok? Third, if yes, how long would the process take?

My many, many thanks.