the adjacency rules of companion says:

It's an addition. A figure in an adjacent space is an adjacent figure, with their distance being 1.

Note that attacking a companion in the same space with a ranged attack requires 1 accuracy, while a non-companion figure attacking an object in the same space requires 0 accuracy - attacks can target objects in the same space, but does not make them adjacent.

A companion follows all normal rules for figures with the following exceptions:

I.e. the normal adjacency rules apply.

@a1bert let me ask you one more question please. I'd like to know if i have the companion already in game, may I activate it, then summon a new one with the ability of the thinkerer and then activate it again in the same card activation?

With the errata, yes.

The Scrap Batallion of each Ugnaught Tinkerer allows the Junk Droid to ready and activate as part of each of their groups. (You activate groups by activating each figure of the group in your preferred order. So, if the Junk Droid is on the map, it can activate before the Ugnaught figure.)

Spot Weld creates a new Junk Droid - if there is one in play, the old copy is removed first. The newly created one must activate after the Ugnaught figure.

Combined these mean that the Junk Droid can activate up to twice per Ugnaught figure, if each Ugnaught uses Spot Weld, but is also created in an adjacent space.

(Technically the Junk Droid is associated with the Ugnaught that created it, but the special rules of Scrap Batallion allow it to activate as part of any Ugnaught group, so the association does not matter.)

1. Activate Ugnaught Tinkerer Group
2. Scrap Batallion readies the Junk Droid
3. Activate the Junk Droid figure - exhausts
4. Activate the Ugnaught Tinkerer figure
Spot Weld create a new Junk Droid - enters the game ready (the old copy is removed just before placing the new one)
5. Activate the Junk Droid figure - exhausts
6. Done with the group activation.

thanks A1bert, that's really great!