Coming in at No 7, Thakur hammered the joint-fastest fifty of the season off 20 balls and shared an entertaining 103-run wicket partnership off 47 balls with Rinku Singh (46 off 33).
In reply, RCB failed to last the distance and folded up for 123 in 17.4 overs with the trio of Varun Chakravarthy, Sunil Narine and debutant Suyash Sharma sharing eight wickets between themselves.
It was KKR’s first win of the season.
Thakur also took one wicket in his all-round show in KKR’s first home match after almost four years.
RCB were going great guns at 44 no loss in 25 balls in pursuit of the big chase before the Sunil Narine triggered the collapse, foxing Virat Kohli (21; 18b) with a beauty in his 150th IPL match.
Chakravarthy then gave a double blow dismissing Glenn Maxwell (5) and Harshal Patel (0) in three balls before ending with splendid figures of 3.4-0-15-4. Thereafter, it was 19-year-old leg-spinner Suyash Sharma (4-0-30-3) who made a dream debut after being included as an impact player in place of Venkatesh Iyer.
The long-haired mystery spinner got two wickets in one over to have KKR reeling at 86/8.
Suyash got his maiden wicket when he deceived Anju Rawat (1) with a tossed up delivery and in space of three balls, he grabbed the prized-scalp of Dinesh Karthik (9) with a fuller delivery.
Fresh from his 82 not out against Mumbai Indians, Kohli teed off in style, scoring a boundary off the first ball of the innings against Umesh Yadav.
At 42 for no loss, the RCB opening duo looked set for another easy chase when Narine triggered the collapse, cleaning up Kohli with a beauty.
The star Indian completely missed the line as the ball sharply turned in to knock his stumps.
Earlier, David Willey (4-1-16-2) and Karn Sharma (3-0-26-2) took wickets off successive deliveries in powerplay and middle overs respectively to give RCB the initial edge.
Willey exposed KKR’s fragile top-order, when the England leftarm pacer knocked over Venkatesh Iyer (3) and Mandeep Singh (0) off successive deliveries.
But RCB frittered away the start with Rahmanullah Gurbaz first taking the charge against a wayward Akash Deep en route to his 44-ball 57, his maiden IPL fifty.
It turned from bad to worse for KKR when a reverse-sweeping Nitish Rana (1) got out following a good review from RCB in the very first ball after powerplay.
KKR looked in trouble at 47/3 but Gurbaz led the charge against the ‘local’ Bengal pacer Akash Deep, pulling him for a six before collecting back-to-back boundaries.
Gurbaz took a review to overturn an LBW decision on 30 and raced to a 38-ball fifty with a powerful sweep over long leg boundary.
But RCB again seized the momentum when the legspinner Sharma had Gurbaz and Russell off back-to-back deliveries in the 12th over.
Thakur then took Akash Deep to cleaners in his knock studded with nine fours and three sixes.
Apart from Willey (4-1-16-2), none of the RCB bowlers failed to impress and Akash Deep conceded 30 runs from his two overs. Siraj also looked wayward and returned with 1/44 from his four overs. They also leaked 23 runs in extras.
