The duo both saw action during this year's RBS 6 Nations but have handed Scotland Sevens head coach Stephen Gemmell a boost ahead of Glasgow 2014 by agreeing to turn out in the abbreviated format.
The versatile Richie Vernon - another full international with 20 caps - is also included.
The Scots are due to take on New Zealand, Canada and Barbados at Ibrox in front of 49,000 fans when the group stage kicks-off on July 26.
Also named in the 12-man squad are skipper Colin Gregor, Roddy Grant, Colin Shaw, Lee Jones, Mark Bennett - a Scotland B cap - James Johnstone, James Eddie, Scott Riddell and Scott Wight.
For Glasgow Warriors back Seymour, this summer's action will be his debut for the sevens side after eight appearances for the full Dark Blues squad.
Lamont, meanwhile, has 86 caps and 12 tries in the 15-a-side format and returns to sevens duties for the for the first time since May 2009, when he played in the final round of the World Series at Murrayfield. He does, however, have previous experience in the Commonwealth Games after competing at Manchester 2002.
Announcing the squad, Team Scotland chef de mission Jon Doig said: "The inclusion of Scotland Sevens always brings a great dynamic to Team Scotland and we are delighted to welcome the 12 players named today.
"Scotland Sevens have shown some excellent form on home soil this season and, with a strong team selection confirmed, we are confident they will give the home crowd a lot to cheer about when they take to the pitch at Ibrox."
Gemmell added: "I have selected a group of players that can be successful at a home games. This is the most important selection I have ever made and the biggest ever for Scotland Sevens.
"The balance of players I have opted for is the strongest combination available to me; therefore, I'd like to thank Scotland, Glasgow Warriors and Edinburgh Rugby for their support.
"I'm delighted to bring in a number of the players who were involved with the top-four finish in the Emirates Airline Glasgow Sevens earlier this month and add to that group with players who have a sevens pedigree or who I believe add value to the squad.
"Firstly, Tommy Seymour is a proven finisher at professional and international level. He has a very good all-round skill set. He is a strong defender, good with ball in the air and he always challenges the opposition defence. He will definitely add value to this group.
"Sean Lamont is a significantly capped international winger - he came through sevens, he has played in a previous Commonwealth Games and he helped Scotland reach the cup semi-final in Murrayfield in 2009. He is one of a number of Glasgow Warriors players who come in from a successful environment at Scotstoun, which will be very positive for us.
"Roddy Grant has cut his teeth in sevens. He brings a wealth of experience, he has previously captained the side and he has had a good season at Edinburgh Rugby.
"I have selected a squad that I believe can build on the success we had at the Emirates Airline Glasgow Sevens in 2014. Being part of a wider Team Scotland is a unique opportunity for all players and management and we will be working hard to ensure we deliver on home soil."
The sevens squad brings the total Team Scotland numbers selected so far to 149, with an anticipated final team in the region of 270 athletes.
Scotland Sevens squad for Glasgow 2014 Commonwealth Games: Richie Vernon, James Eddie, James Johnstone, Roddy Grant, Scott Riddell, Colin Shaw, Lee Jones, Colin Gregor (captain), Scott Wight, Mark Bennett, Sean Lamont, Tommy Seymour.