http://www.d20pfsrd.com/classes/core-classes/monk/archetypes/paizo---monk-a rchetypes/sohei#TOC-Weapon-Training-Ex-
At 6th level, a sohei gains weapon training in one of the following weapon groups, as the fighter class feature: bows, crossbows, monk weapons, polearms, spears, or thrown weapons. He may select an additional group of weapons for every six levels after 6th, to a maximum of three at 18th level. A sohei may use flurry of blows and ki strike with any weapon in which he has weapon training.
http://www.d20pfsrd.com/classes/core-classes/fighter#TOC-Weapon-Training-Ex -
Every four levels thereafter (9th, 13th, and 17th), a fighter becomes further trained in another group of weapons. He gains a +1 bonus on attack and damage rolls when using a weapon from this group. In addition, the bonuses granted by previous weapon groups increase by +1 each. For example, when a fighter reaches 9th level, he receives a +1 bonus on attack and damage rolls with one weapon group and a +2 bonus on attack and damage rolls with the weapon group selected at 5th level. Bonuses granted from overlapping groups do not stack. Take the highest bonus granted for a weapon if it resides in two or more groups.
a) you gain them separately, they are probably tracked separately (as each has a distinct progression), but I'm not entirely sure
I don't think it would be particularly overpowered to let them stack if it's not already RAW
b)RAW it works
