Foreigner property ownership restrictions (except condos)
Foreigner company ownership restrictions (exceptions exist)
Evil and protection - money-wielding foreign gangs are the worst!
Corruption on big projects (a much lesser evil)
Pollution -- choking air pollution on Bangkok roads, mostly due to nonenforcement against a small % of vagrantly violating vehicles !!
Language barrier -- English is poor -- must learn some Thai
Sanitation sometimes poor (avoidable)
Public transport full at rush hour (avoidable)
Weather too hot for some people
Culture too alien for some people
Sometimes unsatisfactory quality of service (like anywhere in the world)
Traffic in Bangkok (not too bad now, was worse before)
Copycat lack of creativity, originality, and double-checking the foreigners or the Thais of higher status / rank