Former Thailand international Therdsak Chaiman has resigned as the head coach of Chonburi after the Sharks could only manage to finish seventh in Thai League 1, which ended on Saturday night.
Therdsak coached Chonburi in the 2016 to 2017 seasons.
Therdsak, who earlier marshalled the midfield for the Sharks before becoming their full-time coach, announced his decision after the team's 2-1 loss to champions Buriram United at their home ground on Saturday night.
"First of all, I would like to thank every football fan who backed me up from the time I took over as the head coach of the team," said Therdsak.
He added: "We finished fifth in 2016, but this season we have slipped to seventh and failed to realise our target.
"I have, therefore, decided to quit and won't be coaching the team in the next season.
"Personally, I have learned a lot over the past two years, but I want a suitable person to come and lead the team now."
Therdsak, a former Thailand midfielder, said he has not made any plans for the future.
"I want to take rest first," he said, "and will make up my mind later.
"I might stay on with the Chonburi team and work in a different capacity or move to another team if there is one interested in me. I will make my decision later."
Therdsak joined Chonburi from S-League team Singapore Armed Forces in 2010.
He had an immediate impact as in his year with the team, he helped the Sharks win the FA Cup in the same year.
He was a regular starter for Chonburi before being appointed as an assistant to then coach Jadet Meelarp in 2015.
He became the head coach of the team in 2016.