@Robert ******
you have to admit it's pretty ambiguous and contradictory. In effect, the Ministry of Labour defines meetings as not requiring a work permit, and thus you can participate in them on any visa. Immigration sees them as work and thus you need a Non-B (or F, in the government sector).
I can tell you that few international companies and organisations sponsor/allow their staff to get visas for short business trips to attend meetings. In fact, the large organisation that I work for more or less has an official policy that it will not sponsor visas for people from visa exempt countries on short business trips to Thailand.