Port drifted further away from the top sides in Thai League 1 as they dropped points again following a 2-2 draw at Samut Prakan City on Saturday night.
Port lacked the needed punch in offence playing without Sergio Suarez, who was suspended, and injured Nelson Bonilla.
Samut Prakan City had a good start as Aris Zarifovic produced the first goal for the hosts in the 18th minute.
Being a goal down, Port switched to attacking mode and saw Bordin Phala being denied by Samut Prakan goalkeeper Patiwat Kummai.
The home team also missed the chance to widen the gap before the break as Chayawat Srinawong's shot went off target.
Samut Prakan were on the front foot again in the second half and nearly got their second goal but Chayawat's header was cleared by Port goalkeeper Worawut Srisupa.
Bordin made the score even for Port at the hour mark, pouncing on a poor clearance by a Samut Prakan defender.
Worawut again came to Port's rescue in the 73rd minute as he warded off a shot by Samut Prakan's Jaroensak Wonggorn before Pakorn Prempak missed a chance for the visitors on the other end.
Port went in front in the 75th minute through a Go Seul-Ki header, but the hosts took only six minutes to draw level with Chayawat delivering the equaliser.
Meanwhile, Pathompon Charoenrattanapirom and Chaowat Weerachart scored after the break to give defending champions BG Pathum United a 2-0 win at Suphanburi.
In the clash of newcomers, hosts Khon Kaen United edged Nongbua Pitchaya 1-0.