Audie -

There so many websites explaining exactly that, in great detail.
Is there some reason you have not already used Google to get your answers?

Excellent question because you included the key words younger and business people.

First, before anything else, I assume you are an adult, Caucasian, man.
Not a student.
Not a poor traveler pinching pennies in order to travel.
Otherwise, we'll have to start over from scratch.
And, if you are Negro, Asian, East Indian, Arab, or a woman of any race, the following won't much apply to you, either.

I'll assume the people you will meet are sophisticated business people with experience in Western countries, or at least, they watch Western movies and TV.
In other words, the people you are meeting are not up-country rice farmers.
Business people in Thailand will, most likely, reach out to shake your hand.
If they do, be very gentle in your return grip.
They are not used to the firm grip we Westerners might expect.

If they don't reach out to shake hands, don't you do it.
They may not know quite how to respond.
You certainly don't want to embarrass anybody on first meeting, especially in Thailand where "face" is such an essential element of social behavior.

Don't "wai", or bow, or put your hands together in front of your chin or anything like that.
The "wai" is not just a greeting, it is a gesture of submission to superior social status.
You are not Thai, so you don't fit anywhere in the Thai social hierarchy.
You don't know anything about it, so don't try to "wai".

Many Thais, especially younger women, will "wai" to you.
You are older, a man (I'm assuming), and you are a visitor, so you will get all kinds of respect.
But never "wai" back.
Just a small smile.
Transpac put it perfectly: But don't smile too much.
You are older; they are younger, so you are the dominant man.
When you get to Thailand look around: people who are socially dominant, even in just the setting of a business meeting, rarely smile.
Smiling is a sign of submission, as well as a form of greeting.
You don't know the social meaning of smiles here, so don't do it.
Just put on a pleasant face, with a hint of a smile.

Now for something you didn't ask, but you need to know if you are coming here on business: eye contact.
In the West, we often associate eye contact with honesty.
If someone won't look us in the eye, we assume he is lying.
Not so in Thailand, and you certainly will have experienced something similar in China.
In Thailand, direct eye contact is considered rude.
It is especially rude, in public, between a man and woman.
In some cases, direct eye contact is considered an invitation to a fight and will generate a response of hostility, but you are not likely to encounter that.
So, expect that even during serious business negotiations, most people will not look at you directly, certainly not often.

Finally, a rhetorical question which goes beyond your original topic.
And your answers are certainly none of my business, but I'll ask as a means of warning.
Why do you want to do business in Thailand anyway?
It's like going swimming with hungry sharks.
They will "wai" to you, smile at you, entertain you in magnificent ways, and provide their women for your enjoyment, before they devour your wallet and anything else of value you bring with you.

By the way, did I mention that I love living in Thailand, but I certainly would never do any business here.

If you have specific questions, you are welcome to send me email or a private message.

-- Peter