Steve Beaglehole’s men, who had Ahmed Musa and Yohan Benalouane among their ranks, were deserved victors, delivering a display typical of their excellent start to the new season.
City started brightly and Blues ‘keeper Marcin Bulka had to be on his toes when Kiernan Dewsbury-Hall’s corner fell perfectly for Sam Hughes, who headed it straight at him.
After 11 minutes, it opened up for Josh Gordon in the middle, so much so for the former Stafford Rangers striker to feel confident enough to test Bulka from 30 yards, but his shot was saved well.
Leicester’s reward for a combative start to the clash came on 25 minutes when Musa broke free of his man to slide it across to Thomas, who finished neatly into the roof of the net.
Beaglehole’s side protected their advantage well but the visiting Blues emerged from the break rejuvenated, going close within seconds of the restart through Isaac Christie-Davies.
But all the drama would ultimately unfold at the opposite end with Thomas putting in another creative display, sitting just behind the forwards in Whetstone.
With 16 minutes remaining, the ex-Coventry man hit a wonderful strike into the top corner to cement City's dominance.
It proved to be an enjoyable affair for the hosts with all among Beaglehole’s squad delivering fine performances against one of the strongest sides in the PL2 pyramid.
Major moment
Wigston-based Thomas joined his home club this summer after helping Coventry lift the Checkatrade Trophy last season and the 20-year-old has impressed many this term.
After a fine breakway goal in the first half, the central midfielder doubled his tally in front of Craig Shakespeare, watching in the crowd, with a brilliant effort from the edge of Chelsea’s penalty area.
It presented the visitors with too tall a mountain to climb in the latter stages and booked City's third win of the fledgling campaign in style.
Who impressed?
On Tuesday night, Academy graduate Hamza Choudhury came off the bench to make his Club debut in Leicester City’s 2-0 Carabao Cup victory over Liverpool.
Following a similar cameo for Josh Knight at Sheffield United in Round 2, manager Shakespeare has proven his willingness to give youth a chance in his first team this term.
Choudhury, who turns 20 on Sunday, did his chances of once again featuring for the senior side no harm at all with another assured captain’s display at Holmes Park.
Where do we stand?
Beaglehole’s men remain fourth in PL2, now level on points with reigning champions Everton, who they defeated 1-0 at Merseyrail Community Stadium last month.
Coming up…
City next welcome Hertha Berlin to King Power Stadium in the Premier League International Cup on Wednesday evening (7pm kick-off).
As with all home fixtures this season, you can follow the action live and free on LCFC TV.
The details…
City: Iversen, Johnson, Pascanu, Hughes, Benalouane, Knight, Dewsbury-Hall (Kaba Sherif 82), Choudhury (c), Musa (Martis 90), Thomas, Gordon (Muskwe 72).
Subs not used: Bramley, Ndukwu.
Goals: Thomas 25, 74.
Chelsea: Bulka, James, Chalobah, Ampadu, Grant, Sammut (c), Sterling, Maddox, Muheim (Hudson Odoi 45), McCormick (Brown 68), Christie-Davies.
Subs not used: Colley, Russell, Da Silva.
Referee: David Richardson.
Attendance: 755