Thompson enjoyed himself in the second half with two tries
Northampton: (13) 37
Tries: Robinson, Tupai, Penalty, Thompson 2
Cons: Spencer 3
Pens: Spencer 2
Border Reivers: (6) 13
Pen: MacRae 2
Northampton earned a valuable Heineken Cup bonus point as they ran in five tries to outclass brave Border Reivers.
Saints dominated the first half and were disappointed to have only a 13-6 advantage thanks to a Mark Robinson try and Carlos Spencer's kicks.
Paul Tupai extended Northampton's lead before Simon Danielli's individual try took the Reivers to within five points.
But Gavin Kerr's yellow card opened the floodgates, as a Saints penalty try was followed by a brace for Steve Thompson.
Northampton's insistence on overcomplicating matters in the backline meant several tryscoring opportunities went begging in the first half, despite their stranglehold on possession.
Spencer's early penalty was followed up by a simple try for Robinson as he took Tupai's pass before sprinting round an unguarded blind-side to cross.
Calum MacRae opened the scoring for the Reivers with a well-struck 45m penalty, but his effort was soon cancelled out by another Spencer success.
Robinson's try set Saints on the road to victory
Ben MacDougall was sin-binned for a high tackle, but an overly ambitious Saints side did not punish his absence on the scoreboard, with MacRae's second penalty cutting the gap just before the break.
Tupai re-established Saints' dominance as he was driven over soon after the break.
But a brilliant score from Danielli, with the winger cutting a superb line to burst through on halfway before beating four Saints players, brought the Borders to just 18-13 behind.
That was the cue for Northampton to up their intensity, and Kerr's yellow card for a scrummaging offence effectively ended the Reivers' resistance.
Moments after the prop departed the field his side conceded a penalty try from a close-range scrum.
Northampton went for the jugular, with Thompson scoring on 64 minutes after being driven over by his team-mates.
And the England hooker grabbed a second when he burst onto a loose ball off a Reivers line-out to burst over.
Northampton coach Paul Grayson
"I am very pleased, that kept the competition alive for us, anything less than five points and we could probably have waved goodbye to any chance of going through.
"Confidence does get dented when you go from a position of strength and feeling pretty good about yourself to having a few losses.
"But, to be fair, the forwards have performed for us in the last three weeks and they got the win for us today."
Borders coach Steve Bates
"We were right in the game until Gavin Kerr was the victim of a very strange yellow card verdict.
"It was all very puzzling because Saints had been committing the same scrummage offences all afternoon.
"That put us under terrible pressure and swung things their way."
Northampton: Vass; Lamont, Davies, Myring, Cohen; Spencer, Robinson; Smith, Thompson, Budgen; D Browne, Gerard; Tupai, Fox, D Browne.
Replacements: J Howard for Davies (47), Tonga'uiha for Smith (75), Hartley for Thompson (76), Lord for Gerard (74), Easter for D. Browne (80).
Not Used: Wyles, Diggin.
Borders: MacRae; Danielli, MacDougall, De Luca, Daniel; Jones, C Cusiter; Kerr, Ford, Kalman; Palepoi, Hamilton; Dalziel, Gray, Brown.
Replacements: Law for De Luca (65), Scott for Ford (67), Douglas for Kalman (46), Newlands for Palepoi (30), Miller for Gray (66).
Not Used: McKearchar, Townsend.
Sin Bin: MacDougall (34), Kerr (58).
Referee: C Berdos (France).