Team Sky's Thomas enjoys almost a two minute buffer over Sunweb's Tom Dumoulin. But is it enough?
Watch the final two stages of the 2018 Tour de France live on SBS from 8.30pm AEST or via the ŠKODA Tour Tracker from 7.55pm.
Tonight the peloton traverses 200 kilometres from Lourdes to Laruns and six categorised climbs.
Two are hors catégorie including all 17.1km gut crunching kilometres of the Tourmalet and its average 7.3 per cent gradient.
The lower half of the final climb, the Col d'Aubisque, is technical and may cause significant gaps for anyone away and descending at this point.
Whether it's Tom Dumoulin and it's two minutes is unlikely. Or Primoz Roglic and two minutes and 47 seconds. Yet, remember what Froome did on Stage 19 of the Giro d'Italia pulling a veritable rabbit out of his hat to almost magic away a three minute and 22 second deficit and win the race?
This is cycling and the Tour de France after all - and a lot has happened at just this edition!
Froome won't - and says he physically can't - challenge team mate Thomas but he must be on the look out for Primoz Roglic snapping at his heels for a podium place - or better - just 16 seconds behind.
Depending on how Stage 19 unfolds, this year's Tour de France could come down to the seconds of the final, 31km individual time trial on Saturday's Stage 20.
Thomas, Dumoulin, Froome and Roglic are all strong time trialists. Again, anything happen.
And until Thomas kisses the Tour de France trophy on Sunday, this race is not over. No doubt Wales will hold its breath until then.
The Tour de France Top 10 after Stage 18:
1. Geraint Thomas (Sky)
2. Tom Dumoulin (Sunweb) +1:59
3. Chris Froome (Sky) +2:31
4. Primoz Roglic (LottoNL-JumbO) +2:47
5. Nairo Quintana (Movistar) +3:30
6. Steven Kruijswijk (LottoNL-Jumbo) +4:19
7. Mikel Landa (Movistar) +4:34
8. Romain Bardet (AG2R) +5:13
9. Dan Martin (UAE Emirates) +6:33
10. Jakob Fuglsang +9:31
Watch these two crucial stages live on SBS from 8.30pm AEST or via the ŠKODA Tour Tracker from 7.55pm.
Then, join the peloton's procession to Paris on the final stage live from Sunday 11.30pm AEST on SBS or via the ŠKODA Tour Tracker.