How would anyone know that one person in the group was the 'manager'? If it were just a large family on holiday the 'father' would typically be in charge, but he wouldn't have any special visa.
My solution to that (after 9 years here mostly on Tourist visas) is to set up a Thai company and launch a business here.
It took a couple of years to identify the right business and its taken longer than I planned to raise funding to get it off the ground, but I'm closer to the finish line (starting line?) with planned launch now in Q1 2018.