Scarlets back-row Thomson, who played for New Zealand at under-20 level, and Exeter Chiefs lock Skinner are eligible through family connections but are among just three new caps in an expansive squad named by coach Gregor Townsend on Wednesday.
The third is Glasgow centre Sam Johnson, a former Australian schoolboy international who played Super Rugby with the Queensland Reds before moving to Scotland, and qualifies on residency grounds, having joined the Warriors three years ago.
All three are in line to make their debuts in one of the November tests against Wales, Fiji, South Africa or Argentina.
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"We now begin the last 12 months of our preparations for the World Cup with four tests in four weeks, a similar challenge to the one we'll face in Japan," Townsend said in a statement from Scottish Rugby.
"We've named a 40-man group for this campaign, which highlights the quality of player that is now available to us and the competition for places.
"It also enables us to welcome more players into our training environment and hopefully give a few more players a taste of test rugby.
"It's going to be an exciting year for the squad but our primary focus is fixed on performing well against Wales -- familiar opponents who have already recorded a win against us this year."
Scotland face Wales in Cardiff on Nov. 3 and then play at their Murrayfield home against Fiji on Nov. 10, South Africa one week later, and Argentina on Nov. 24.
The Scots have been drawn alongside hosts Japan in Pool A at next year's World Cup, in a group that also contains Ireland, Russia and Samoa.
Squad:
Backs: Alex Dunbar (Glasgow Warriors), Dougie Fife (Edinburgh), Chris Harris (Newcastle Falcons), Adam Hastings, George Horne, Pete Horne, Sam Johnson, Huw Jones, Lee Jones (all Glasgow Warriors), Blair Kinghorn (Edinburgh), Greig Laidlaw (Clermont Auvergne), Sean Maitland (Saracens), Byron McGuigan (Sale Sharks), Ali Price (Glasgow Warriors), Henry Pyrgos (Edinburgh), Finn Russell (Racing 92), Matt Scott (Edinburgh), Tommy Seymour (Glasgow Warriors).
Forwards: Alex Allan (Glasgow Warriors), Simon Berghan, Magnus Bradbury (both Edinburgh), Fraser Brown (Glasgow Warriors), Allan Dell (Edinburgh), David Denton (Leicester Tigers), Matt Fagerson (Glasgow Warriors), Ross Ford, Grant Gilchrist (both Edinburgh), Jonny Gray, Rob Harley (both Glasgow Warriors), Murray McCallum, Stuart McInally, WP Nel (all Edinburgh), Gordon Reid (London Irish), Jamie Ritchie (Edinburgh), Sam Skinner (Exeter Chiefs), Blade Thomson (Scarlets), Ben Toolis (Edinburgh), George Turner (Glasgow Warriors), Hamish Watson (Edinburgh), Ryan Wilson (Glasgow Warriors).
(Reporting by Mark Gleeson; Editing by John O'Brien)
