"I would like to end my role as coach of the Thailand team and will clear my work for the organisation in 90 days," Kiatisak said in a posting on his @coach_zico Instagram account on Friday, referring to the Football Association of Thailand (FAT).
"I would like to thank all the players, my coaching staff, football fans and my family who are always behind me," he added.
Kiatisak, nicknamed Zico, signed a new one-year contract with the FAT on Feb 27.
But FAT president Somyot Poompunmuang on Thursday called the side's two recent losses against Saudi Arabia and Japan "embarrassing" and indicated there needed to be a change (read more here).
Thailand lost 3-0 to Saudi Arabia at home on March 23, followed by a 4-0 defeat by Japan on Tuesday in Saitama.
The War Elephants have earned only one point from their campaign to qualify for a place in the World Cup finals in Russia next year.
"The team has just one point from seven matches and I, being the coach, have to assume responsibility for it," Kiatisak, 33, said earlier on Friday. "The FAT has the right to be unhappy about it, but I think the Thai football fans understand this."
Zico's followers on Instagram were quick to offer support to the popular former player, who led the national side to the SEA Games championship in 2015 and the Suzuki Cup title in 2014 and 2016. Kiatisak also earned 131 caps and scored 70 goals for his country between 1992 and 2007.
"Thank you for everything and for making Thailand football come this far with discipline," one follower named bam9876543 wrote.
Somyot has been busy fending off rumours that he planned to sack Kiatisak since the team returned from Japan.
Earlier on Friday he said no decision had been taken and that he hoped to hold talks with his coach and others involved on April 10 about the team's future direction.
He also also dismissed reports that the FAT had been receiving applications from foreign coaches. "We have a website which can be reached through hotlinks on the Fifa, AFC and AFF websites," he said.
"We have received profiles of coaches from Argentina, Spain, Brazil, Croatia, Bolivia and Italy but it is a routine thing," Somyot added.
Read original story here.