The surprise omission is Cardiff Blues back Rhys Williams, while Ruddock has been unable to consider six players for the All Blacks opener on Saturday week, including British & Irish Lions trio Gavin Henson, Tom Shanklin and Ryan Jones.
Ruddock said: "Lee has hit the headlines in recent weeks with a string of outstanding performances for the Scarlets to fully justify his selection.
"He is a hugely exciting footballer who has the pace and size to break through opposition defences.
"He has a fantastic left foot, can play in more than one position and has been given the nod over Rhys Williams because of his rich vein of form.
"The door is not closed on Rhys, nor anyone else who performs well in forthcoming games and we will add to the squad as and when necessary."
Thomas regains the captaincy from Michael Owen after missing Wales' final two games of their Six Nations Grand Slam season due to injury.
Owen skippered Wales against Scotland and Ireland, while centre Mark Taylor did the job on tour in the summer.
"Gareth proved what a great leader he is last season. He is an inspiration within the squad - a real energiser and someone who leads by his own shining example," added Ruddock.
"There is no doubt his experiences of playing in France and on the Lions tour have given him an insight into the make-up of top international players from other countries and that experience will help us in our challenge to beat the best in the world."
Wales open their demanding November series against New Zealand, followed by appointments with Fiji, South Africa and Australia.
The All Blacks, Springboks and Wallabies fixtures are already 74,000 sell-outs with more than 40,000 tickets sold for the November 11 Fiji match.
"If you want to be the best, you have to play and beat the best," added Ruddock.
"We have risen to fifth in the IRB world rankings thanks to last season's Grand Slam but over the next month we have to face three of the teams ranked ahead of us."
Wales squad for autumn Tests against New Zealand, Fiji, South Africa and Australia:
Backs: L Byrne (Llanelli Scarlets), G Thomas (Toulouse, capt), K Morgan (Newport Gwent Dragons), C Czekaj (Cardiff Blues), S Williams (Ospreys), M Taylor (Sale Sharks), S Parker (Ospreys), M Watkins (Llanelli Scarlets), C Sweeney (Newport Gwent Dragons), S Jones (Clermont Auvergne), N Robinson (Cardiff Blues), D Peel (Llanelli Scarlets), G Cooper (Newport Gwent Dragons), M Phillips (Cardiff Blues).
Forwards: D Jones (Ospreys), J Yapp (Cardiff Blues), A Jones (Ospreys), R Thomas (Cardiff Blues), M Davies (Gloucester), H Bennett (Ospreys), B Cockbain (Ospreys), I Gough (Newport Gwent Dragons), R Sidoli (Cardiff Blues), L Charteris (Newport Gwent Dragons), C Charvis (Newcastle), J Thomas (Ospreys), M Williams (Cardiff Blues), R Sowden-Taylor (Cardiff Blues), M Owen (Newport Gwent Dragons, vice-capt), A Popham (Llanelli Scarlets).