England ran in 10 tries in total, with flanker Gus Jones (4), Thacker (2), Henry Taylor, Zach Kibirige, Alex Lundberg and Maro Itoje on the scoresheet. Fly-half Billy Burns added 15 points with the boot, and Sam Olver kicked a conversion.
The home side were already 10-0 up when Thacker scored his first from close range after Jones had made a dart for the line, and he scored his second before half-time as England led 38-0 at the break.
That advantage stretched to 67 points before Wales grabbed their only score of the evening from a penalty try.
Thacker was replaced in the 52nd minute, while Tigers colleague Henry Purdy also started the game, being replaced on the hour.
Head coach Nick Walshe said: “It was an excellent performance, and not too far off perfect, particularly in terms of the way we transferred what we have done on the training ground on to the pitch.
“There is, of course, still much to work on, but it was a great display. The Championship is still out of our hands but all we can do is perform as well as we can.”
England Under-20
15 Howard Packman (Northampton Saints)
14 Zach Kibirige (Newcastle Falcons)
13 Nick Tompkins (Saracens)
12 Harry Sloan (Harlequins)
11 Henry Purdy (Leicester Tigers)
10 Billy Burns (Gloucester Rugby)
9 Henry Taylor (Loughborough University)
1 Danny Hobbs-Awoyemi (Northampton Saints)
2 Harry Thacker (Leicester Tigers)
3 Scott Wilson (Newcastle Falcons)
4 Maro Itoje (Saracens, captain)
5 Tom Ellis (Bath Rugby)
6 Ross Moriarty (Gloucester Rugby)
7 Gus Jones (London Wasps)
8 Joel Conlon (Exeter Chiefs)
Replacements:
16 Tom Woolstencroft (Bath Rugby) for Thacker 52 mins
17 Alex Lundberg (London Wasps) for Hobbs-Awoyemi 62 mins
18 Paul Hill (Leeds Carnegie) for Wilson 62 mins
19 Jonny Hill (Gloucester Rugby) for Ellis 68 mins
20 Hayden Thompson Stringer (Saracens) for Moriarty 60 mins
21 Stuart Townsend (Exeter Chiefs) for Taylor 58 mins
22 Sam Olver (Northampton Saints) for Burns 54 mins
23 Aaron Morris (Bedford Blues) for Purdy 60 mins
