By Gabriel Tan at the Jurong West Stadium
Shi Jiayi opened the scoring for Singapore in the second minute with a blistering shot that Kamran Khan failed to keep out on the line, before Khairul Amri capitalised on an error from Jaffar Khan to make it 2-0.
The Lions then wasted a number of good chances to add a third, before Shahril Ishak and Aleksandar Duric added goals in the final 13 minutes to give Radojko Avramovic's men a badly-needed victory ahead of Sunday's Suzuki Cup Group B opener against Malaysia.
Having won just two of their last 13 outings, the Lions headed into their final warm-up game before the biennial regional meet desperately needing a win but two minutes in, Shi got them off to a perfect start when he latched onto a neat pass by Shahril and burst down the right before drilling in a low shot that was helped over the line by Kamran.
Shahril then had a chance of his own five minutes later when he picked up the ball on the right and cut inside Muhammad Ahmed, before drilling in a shot that deflected off Kamran but fortuitously smashed into the wrong-footed Jaffar.
Buoyed by their fast start, Singapore began to dominate proceedings and came close again in the 19th minute when Shahdan Sulaiman latched onto a brilliant through-ball by Mustafic Fahrudin and raced towards goal, only to place his effort inches wide of the far post.
Three minutes later, Amri wasted a fantastic opportunity to double his side's lead when he was picked out unmarked inside the area by Shahdan but somehow managed to fire wide from four yards out.
However, the 27-year-old made amends on the half-hour mark when he was handed a goal after a comical error from Jaffar. The Pakistan Army custodian appeared odds-on to claim a hopeful pass from Shahril but inexplicably let the ball slip under him, leaving Amri with the simplest of tap-ins.
Despite now having a comfortable lead to sit back on, Singapore continued to press forward after the break and should have added another in the 52nd minute when Duric, who came on at halftime for Amri, met a corner from Shahdan with a near-post header that was way over.
Four minutes after the hour mark, the hosts did put the ball into the back of the net for a third time when Shahril raced onto a terrific pass by Mustafic and cut inside a challenge before curling a shot into the far corner, only for the strike to be chalked off by the linesman's flag.
However, there was to be no denying the Lions skipper in the 77th minute when he extended his side's lead by sweeping home a cross from Shahdan, after an error from Muhammad Ahmed had handed the midfielder acres of space to exploit down the right.
Although the result was now all but settled, the visitors could have added a consolation three minutes later when Kalim Ullah slipped in behind the opposition defence and rounded the onrushing Izwan Mahbud, only to see his goal-bound attempt cleared off the line by the recovering Daniel Bennett.
Instead, it was the Lions who found the back of the net once more two minutes from time when Mustafic split apart the visitors' backline with another slide-rule pass to release Qiu Li, who proceeded to slide the ball across the six-yard box for Duric to tap home.
Singapore: Izwan Mahbud (Joey Sim 85'), Daniel Bennett, Safuwan Baharudin (Irwan Shah 50'), Baihakki Khaizan, Shaiful Esah, Mustafic Fahrudin, Hariss Harun (Isa Halim 71'), Shahdan Sulaiman, Shi Jiayi (Qiu Li 66'), Shahril Ishak (Fazrul Nawaz 78'), Khairul Amri (Aleksandar Duric 46').
Pakistan: Jaffar Khan (Yousef Ejaz Butt 46'), Samar Ishaq, Kamran Khan, Zesh Rehman (Omar Malik 67'), Muhammad Ahmed (Faisal Iqbal 81'), Muhammad Adil (Saeed Ahmed 67'), Zia Us Salam, Naveed Ahmed (Muhammad Ali 46'), Shabir Khan, Hassan Bashir, Kalim Ullah.