Page 6 of English rules:
Expanding through new Conquests
> Ready your Troops
Leaving in place one Race token in each Region they occupy, the player may take all his other Active Race tokens from the map back in hand and use them to conquer new Regions.
> Abandoning a Region
Only those Race tokens that were taken back in hand may be used to conquer new Regions. If a player wishes to free up some more Race tokens, he may opt to entirely empty up some - or all - Regions, leaving no Tokens there; but in this case, these now abandoned Regions will no longer be considered his, nor bring him any Victory coins.
Emphasis mine. Now about using those tokens:
All rules relative to the conquest of a new Region (see Conquering Regions, p. 4) must be respected, with the exception of the rule relative to the First Conquest - which only applies to new races entering on the map.
And in the mentioned place, the rules say:
2. Conquering Regions
The player's Race tokens are used to conquer Regions of the map, whose occupation will yield Victory coins for that player.
> Conquering a Region
To conquer a Region, a player must have available to deploy: 2 Race tokens + 1 additional Race token for each Encampment, Fortress, Mountain, or Troll's Lair marker + 1 additional Race token for each Lost Tribe or other player's Race token already present in the Region.
> Following Conquests
The active player can repeat this process to conquer as many new Regions as he wishes during his turn, provided he has enough Race tokens left to accomplish these successive conquests.
Thus the bold text in the quotation above states that only the tokens, obtained in Ready your troops phase can be used to expand. Moreover, the rules of conquest say, that this can be done as long as there are enough tokens available. So all the tokens, picked up in Ready your troops phase can be used. There is no mention in the rules about the relation between a region, token is picked up from, and a region token is conquering. So any picked up token can be used to conquer any region. And yes, in some cases (e.g. Amazons) you can "pick up" tokens outside the board.