The Kirins were hoping to get back on track following a 2-1 loss to Kashima Antlers in the AFC Champions League (ACL) last week and a shocking 1-0 defeat at struggling Thai Honda at the weekend.

Things were going to plan when Teerasil Dangda opened the scoring with a penalty in the 39th minute. But a sensational six-minute spell saw Port FC turn things around.

Josimar Rodrigues scored either side of a Sergio Suarez header to make it 3-1 for the visitors at half-time.

Teerasil pulled one back in the second half but the champions missed their 12th man, and they could not get the elusive equaliser.

Muang Thong again shuffled the pack, with next week's ACL Round of 16 clash with Kawasaki Frontale in mind as fringe midfielders Sanukran Thinjom and Sorawit Panthong both made rare starts.

The hosts took control early on and came very close in the 12th minute when Lee Ho headed Theerathon Bunmathan's corner off the bar. Minutes later, Theerathon had a free-kick opportunity, but his effort sailed over.

Muang Thong then hit the woodwork for a second time when Wattana Playnum was sent clear. The midfielder scuffed his shot, but it beat Worawut Srisupha in the Port goal before coming back off the post.

At this stage, it just looked like a matter of time before the home made the breakthrough. But they had to wait until the 30th minute before threatening the Port goal again.

First, a neat move between Sorawit and Teerasil Danga released Sanukran on the left, but Worawaut did well to narrow the angle and beat out the midfielder's powerful strike.

Muang Thong picked up the loose ball and it was fed inside to Chanathip Songkrasin on the edge of the box. The playmaker struck a fierce right foot shot that Worawut had to tip over the bar.

But the champions were handed the opportunity to open the scoring in the 38th minute when Teerasil was brought down by Elias Dolah on the edge of the box. The contact seemed to take place marginally outside the box but the referee had no hesitation in awarding a spot-kick.

Theerathon stepped up and fired it high beyond Worawut to give Muang Thong a deserved lead.

Port tried to hit back immediately and forced a couple of corners, before Panphanpong Pinkong swung in a cross from the left. Naoaki Aoyama failed to clear properly and the ball broke for Josimar, who smashed the ball home on the half volley from 16 yards.

Two minutes later, Panphanpong put in another excellent ball from the left and Sergio Suarez rose unmarked at the far post to head past Kawin.

The Muang Thong defence were again static a minute later when Pakorn Prempak crossed from the right and Josimar was given time and space to volley home two minutes into added time.

It was an incredible turnaround. From being in complete control and 1-0 up, Muang Thong went in two goals down at the break. Head coach Totchtawan Sripan took action by withdrawing his two young midfield men and replacing them with the experienced Thai internationals Adisorn Promrak and Mongkol Tossakrai

As expected, the league leaders came out on the front foot after the break and Teerasil flashed a shot just wide from 20 yards.

Five minutes later, the Thailand striker looked certain score when Theerathon's cross found him alone in front of goal six yards out. But Teerasil failed to attack the ball properly and it simply skimmed off his forehead and wide.

On the hour mark, a probing move by Muang Thong ended with Chanathip collecting the ball on the edge of the box and curling in a shot which looked headed for the top corner before Worawut clawed it wide.

From the resulting corner, Aoyama jumped highest but his powerful header came crashing back off the bar.

Two minutes later, Muang Thong finally pulled one back, though the assist came from an unlikely source. Centre-back Celio Santos exchanged passes with Chanathip and made a surging run down the left before cutting back for Teerasil to tap into an empty net.

The visitors' tactic of sitting back and letting the Kirins attack them was beginning to look misguided as it looked inevitable that the hosts would level the score sooner or later.

But, out of nowhere, Port almost grabbed a fourth. An excellent ball from Pakorn on the right found its way to Josimar at the far post, but the Brazilian just failed to connect with his outstretched boot.

As the game moved into the final 10 minutes, Muang Thong were growing frustrated and momentum had slowed. When Aoyama headed over from Tristan Do's corner in the 86th minute, it seemed that the hosts were beginning to lose hope.

Kawin pushed forward in desperation at a late corner kick, but Port held on for a memorable win. The champions now have to look over their shoulders again as Buriram United's 3-0 win over Suphanburi edged them just one point off top spot.

They at least have the consolation of playing in front of their fans on Saturday when Ubon UMT United visit.