Given the profile you describe, I'd go to BKK, stay in a decent hotel on the river near a river express landing http://www.into-asia.com/bangkok/boats/ , and scout for a longer follow-on trip to Siem Riep for a visit to the Angkor site.

For the truly adventurous, go overland from Bangkok to Cambodia. An authoritative site is: http://www.talesofasia.com/Cambodia/Overland/index.htm

Beijing and Shanghai are good destinations, each quite different. Angkor, however, is somewhat "perishable," in that it will be overrun by tourists before too much longer.
Rich

[This message has been edited by rjh (edited 07-05-2002).]