No
"Extraordinary Ability" is not a type of action. You can have Extraordinary Abilities that give you passive bonus to some rolls, that require some action to be activated, or many other things.
Quick explanation
For the Leshy case, it has two attack mode: slam and seed. The fact that the seed attack is an extraordinary ability doesn't change anything. As the two attacks are listed separately:
Melee slam -1 (1d3-2 plus ensnare)
Ranged seed +3 (1 plus ensnare)
They are separate attacks that can't be used at the same time.
Long explanation
In general natural attacks can only be used with other natural attacks, or with weapons, in which case the following rule applies:
Creatures with natural attacks and attacks made with weapons can use both as part of a full attack action (although often a creature must forgo one natural attack for each weapon clutched in that limb, be it a claw, tentacle, or slam). Such creatures attack with their weapons normally but treat all of their available natural attacks as secondary attacks during that attack, regardless of the attack’s original type.
The seed attack is not a natural attack (or it would be specified as "seed" does not figure among standard natural attacks). I guess you can read the seed attack as a weapon attack (it seems like that's not at all intended but the rules are vague enough so the doubt is permitted), but in that case keep in mind your slam attack will become secondary. What is more likely is that the seed attack is neither one or the other, like the special attacks you can get when casting ray spells. These attacks typically can't be used as part of a full-round.