Jires Ekoko hit the visitors' opener in the fifth minute and Asamoah Gyan made it two seven minutes before the break as Al-Ain pulled clear of second-placed Al-Jazira, who closed to within four points after Saturday's win at Al Wahda.
Baniyas are up to fourth after a 3-1 win at home to Al-Wasl.
The hosts led 2-0 at the break through Andre Senghor (26) and Mohammed Fawzi (28), and although Al-Wasl got back into the match through Mahmoud Shikabala in the 61st minute, Senghor's second three minutes later put the game to bed.
Boris Kabi hit a hat-trick as Ajman romped to a 4-1 win at Dibba Al Fujairah.
Karrar Jassim set the ball rolling for Ajman in the 13th minute while Kabi opened his account three minutes before the break.
Abdul Al Hassan reduced the deficit in the 71st minute, but Kabi struck again seven minutes later and added his third in added time to wrap up a comprehensive win.
Dubai SC and Al-Ittihad Kalba shared a 1-1 draw in the day's other game.
Gregory du Frenice fired visiting Kalba ahead from the penalty spot in the 31st minute but the game ended honours even as Ali Hassan struck for Dubai seven minutes later.