I was always told that for foreigner to start business in Thailand, it was necessary for it to be owned by Thais or majority of shareholders to be Thai. My friend who is visiting from USA says because of reciprocal agreement with US, Americans can start business here under own name. Is this true?

The answer is yes with some provisos.

If you do a Google search for Amity Treaty you will find necessary info.

My friend who is visiting from USA says because of reciprocal agreement with US, Americans can start business here under own name. Is this true?

Use google to find the web site of the us embassy in bangkok. go to their publications page where you will find some excellent reference material including an annually-updated thailand country profile. look for references to treaty of amity and economic relations.

Also use the thaivisa search function to identify the many many previous threads on this issue

Yes, the Amity Treaty is just one of the topics that should have a pinned thread, as Khun Jean has alluded to. Maybe the pinned threads "Job Offers, "Jobs Wanted", and "Business Classifieds" could all be moved to the Classified Ads section to make room for it.

I did as you suggested and found info on google. Thank you for the assistance.