Defending champions Tampines have been inconsistent so far this season but arrested their alarming slide last week with a 2-0 win over Home United.
However, their midweek home defeat to Terengganu suggested that Rovers' problems might not exactly be completely over, although they resoundingly answered those doubts on Friday evening.
Captain Aleksandar Duric put them ahead after 12 minutes, only for Slovak midfielder Josef Kaplan to equalise for the Eagles three minutes before the break.
Nonetheless, Ahmed Fahmie netted a minute later to ensure Tampines went in ahead at the break, before they put Geylang to the sword in the second half, with Duric adding two more to complete his hat-trick, while Mustafic Fahrudin grabbed one of his own.
On Friday, DPMM FC stayed top of the table with an unconvincing 1-0 win over Courts Young Lions, while Balestier Khalsa recorded an impressive 2-1 victory at Albirex Niigata.
Thursday's only game saw SAFFC's ailing title hopes take another blow after they were held to a 2-2 draw by Woodlands Wellington.
Saturday's Great Eastern-YEO's S.League Results
Geylang United 1-5 Tampines Rovers
Friday's Great Eastern-YEO's S.League Results
Thursday's Great Eastern-YEO's S.League Results
Sunday's Great Eastern-YEO's S.League Fixtures
Home United vs Harimau Muda
Gombak United vs Hougang United