City dominated the early possession but didn't take a first shot at goal until Nabbout received the ball on the right from Marco Tilio in the 22nd minute.
The winger cut inside and unleashed a rocket of a left-foot strike into the back of the net from outside the box, City's match report says.
The home side fought back, and an equaliser came quickly when Teerasil Dangda was on the spot to net home a perfectly placed cross from Pathompol Charoenrattanapirom.
Despite several good chances for both sides in the second half of their group G ACL match, neither team found a winner, said head coach Patrick Kisnorbo.
He was pleased with the start to their ACL campaign.
"At the end of the day, we could've scored at the end, we had a few good half chances but , first and foremost for us, it's a good start to our campaign."
"We know that it's not going to be a perfect game. We're not going to be able to press for 90 minutes, we're not going to have possession for 90 minutes and that's reality. The way we handled it, I thought we did really well."
City is hoping to end Australia's recent difficult run of results in Asia.
Tony Popovic's Western Sydney Wanderers claimed the 2014 title, while Adelaide United reached the final in 2008.
But since the Wanderers' triumph, no Australian team has gone further than the competition's round of 16.
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