Thornlie managed 235 runs on day 1, including a huge 104n.o. from Kodie McKrill.
Despite seven of the 11 batsmen being dismissed for seven runs or less, McKrill and teammates Alan Zanich (54 runs), Stephen Bennett (24) and Brad Fletcher (22) proved harder to knock over.
Nick Siave and Elliott Lawrie did most of the damage with the ball, taking seven wickets between them.
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But it was with the ball where Thornlie did the most damage.
East Fremantle were sitting at 2-7 and then 5-20 as they tried to chase down 235.
They looked like they would struggle to make it into triple figures before a 90n.o. from Siave helped the team to a more respectable 161.
Siave and opener Daniel Allsworth (15) were the only batsmen to reach double figures, while Thornlie’s Ryan Jenkins took a brilliant 6-30.