You can't conduct any type business on a tourist visa you will be deported if you are caught. People have been warned that they will be deported for singing on a karaoke in clubs as it's classed as work.
The business visa you are talking about (NON-B) is designed for employees of foreign companies who are conducting business with Thai companies. Not foreign businesses conducting business alone or with each other.
In fact without evidence of this you won't even get your NON-B visa.
Are you sure you can do business meetings on a tourist visa? On a business visa is fine of course as you've declared that your intention is to be there for business, but having a business visa also require you to have a company that is sending you there on business before hand. Plus, I'm not sure how long of a stay you'd normally get with a business visa.
With a tourist visa, I think you're strictly not supposed to perform any business activities. You might be able to pass off your meeting as a "casual chat" if you want to risk it.
In the countries I've been to the business travel visas are the same as the tourist ones, you just have to declare you are there for business purposes also. So the length is the same, 3 months.
I know colleagues (engineers) who were detained and kept under "hotel arrest" in Indonesia for being on the customer site without the correct working Visa (our guess - a tip off)
I worked in Thailand on assignment for a large company there and we got a wind that the authorities where going to come in on a certain day and check every single foreigners passports. We were told even that we had the correct Visa, work from home that day.
In Japan you can get a 3 month tourist visa on entry. I know many who have worked on the customer site with this. Once again - illegal, all it takes is a tip off from a local employee and your in big, big trouble.. don't expect to ever visit that country again.
I know someone who was working in Sweden without the correct Visa - a local employee (part of a work union) reported him.
There appears to be a fine line between "business" (meetings etc) and actually doing productive work for a company entity based in Japan. I don't have clarification on this, and this is only second hand information.
On a different note, they do check the frequency of re-entries (on a tourist visa) as I know of one peer who was put into a room at the airport and questioned after re-entering a few times in one year. So if your "doing business" a couple of times a year with a few months in between, it may still look suspect.
Additionally I know of a guy's wife who was deported on re-entry after the 3rd time. She wasn't working and was banned from re-entring for 11 months.
The probability may well be very low - There could be a statistical influence in why I have all these 'stores' due to being required to travel 70-80% for my employment for the past 5 years.
If you read blogs on these types of things you are only going to see the 'worst case scenarios' as the majority of people with positive experiences are unlikely to rush to their PC and write a glowing post about their Visa experience...
2. You can do business meetings from a co-work office.
Now please tell me how being in a co-work office, working for a company incorporated abroad and not accepting local payments, can get one arrested.