An early misplaced pass handed Coutinho the chance to run at the Thailand defence and the Brazilian obliged, shrewdly dribbling through the opposition backline before slotting home to give Liverpool the lead.
Although the first-half petered out, Liverpool flew out of the blocks in the second and doubled their advantage when Aspas slotted home before Gerrard added a third with a deft chip after being laid on by the Spaniard.
Luis Suarez’s introduction on the hour almost handed the visitors a fourth but the unsettled striker’s header crashed against the crossbar.
Thailand enjoyed plenty of possession throughout and tested Simon Mignolet a couple of times from distance, but they had their own goalkeeper Kosin Hathairattanakool and the woodwork to thank for keeping the score respectable.
Aside from the glaring absence of Suarez, Brendan Rodgers fielded a strong team and Liverpool started brightly with Gerrard and Coutinho orchestrating the early proceedings.
And it was the Brazilian who created the first opening, wriggling clear of the challenges to set up Aspas whose fierce shot was deflected over by a desperate defensive lunge.
Glen Johnson then whipped a cross towards the near post which was met by the outstretched leg of Fabio Borini but saved by Hathairattanakool at close range.
Liverpool made the breakthrough inside 20 minutes when Thailand needlessly gifted possession inside their own half. The ball broke to Coutinho who expertly dribbled past a mass of Thailand shirts before cutting inside and slotting into the bottom corner.
The hosts responded well and began to spray the ball around confidently, forcing Mignolet into a few saves from distance, but the heat started to take its toll on the players and soon the first-half had fizzled out as a spectacle.
Liverpool looked to start the second-half with the same intensity as the first, and quickly notched another goal when Aspas found himself in behind the Thailand defence and comfortably slotted home.
The Spaniard then turned provider for the third, finding Gerrard after being forced wide before the England international delivered a clever chip over the stranded keeper.
The introduction of Suarez caused the Rajamangala Stadium to erupt, his first touch greeted like a goal, as Liverpool freshened up their attack for the final half hour.
And the Uruguayan almost scored immediately when he rose to meet Gerrard’s free-kick, only to see his header crash back off the bar.
Substitutes Jordon Ibe and Jordan Henderson then combined inside the area, the latter forcing Hathairattanakool into a low save down to his left before Ibe lashed wide with teammates better placed.
Gerrard then found himself through on goal as full-time approached but his tame effort was saved before he saw his whipped effort agonisingly find the underside of the crossbar as Liverpool pressed for a fourth.