Port FC coach Jadet Meelarp said star defender Adisorn Promrak will not be guaranteed a starting spot following his move from fellow Thai League 1 club SCG Muang Thong United.
Thailand defender Adisorn completed his switch from the Kirins on Friday.
Jadet admitted the addition of the Thailand star will strengthen Port's defensive unit, but insisted that the 26-year-old would not jump into the starting line-up when the domestic season resumes in September.
"We will have to wait and see how he does during training with the team. No-one is guaranteed of a starting spot at this point, and that included players such as Elias Dolah and David Rochela," said Jadet.
Port players will return to training in July, added the coach. They will have around six to eight weeks to prove themselves. Port were joint third in Thai League 1 after four games when the season was suspended in March.
They and BG Pathum United have 10 points, two behind pacesetters Bangkok United and Ratchaburi. Muang Thong are seventh on six points.
Port won the FA Cup last season for their first trophy in a decade.
Meanwhile Muang Thong chairman Viluck Lohthong revealed it was the player's decision to leave the club.
Apart from Adisorn's departure, another Thailand star Sarach Yooyen has been in talks to join BG Pathum United.
"Sarach's negotiation with BG Pathum United is likely to be finalised within a few days," he said. "It is the club's priority to find their replacements and it will be big names who come in."