Non-Imm Os are harder to get now than they used to be, so I am probably going to try a "business visa" (I think the lady at the consulate called it that) because all they need is a letter from a business in Thailand requesting that I be allowed one.

Before I do this, I just want to know if there are any pitfalls. For instance, will anyone on the Thai side need any documentation once I arrive in Thailand? What about when I leave the country and come back to get another stamp?

From my understanding, all they will need at the consulate is a letter (well, plus money, passport, etc). To my knowledge, I won't ever need anything else (a work permit, etc) - in fact I don't actually plan to be working, I just need a decent visa.

Please comment. Thanks.

Depend on consulate.

In SE asia you must provide a WP3 (receipt for application for work permit).

Some consulate in Europe and Australia still issue non-B visa with only invitation letter from Thai company.

I think the WP3 is only needed if you are working in Thailand. If you want it on the basis on doing business in Thailand, it would not be required.

If you get the visa in your home country, you may be able to get it with just the invitation letter. But many consulates require more.

For the Guangzhou consulate you need:

5 passport pictures

2 copies of passport

2 copies of application

Invitation letter

Tax Registration of company

List of shareholders in company

Business registration of company

All of these need to be stamped with the company stamp and signed by an officer of the company. Then you also need a copy of the person signing the documents ID card. This also needs to be signed.