Japanese Nishino, who oversees the Thai senior and U23 national sides, began his reign in Thailand in July last year and the current contract expires at the end of this month.
The new deal will be signed at a press conference tomorrow (Jan 24), Somyot said.
Under Nishino, the Thai senior team got off to a decent start in Asia’s second qualifying round for the 2022 World Cup.
The U23 side, who were three-time defending champions, suffered a first-round exit at the SEA Games last month.
However, the junior War Elephants bounced back by reaching the quarter-finals before losing to Saudi Arabia at the ongoing AFC U23 Championship.
Thanks largely to Thailand’s performance at the AFC U23 event, Nishino received a new contract.
Somyot said it takes time for Thailand to reach another level but the national teams under Nishino, particularly the U23 team, have had satisfying results.
He declined to discuss Nishino's salary.
Nishino said: “When I decided to coach Thailand, I knew that it would be difficult and challenging. The job has not been very smooth but I think Thai players have potential. We have to keep developing.
“I’d like to see better results from the Thai teams. The FAT wants to see Thailand go to the 2026 World Cup and I want to be part of the team. I want to help lift the standard of Thai football.”
Asked about the qualifying round for the 2022 World Cup, Nishino said Thailand had to win all three remaining Group G matches to stand a chance of advancing to the next qualifying phase.
Thailand host Indonesia on March 26, travel to the UAE on June 4 and are at home against Malaysia on June 9.
Vietnam lead the group ahead of Malaysia and Thailand.
The eight group winners and four best runners-up progress to the continent’s 12-team final qualifying stage for Qatar 2022.
“We have no other option but to win the three remaining matches. We will have two games at home,” Nishino said.
"We will have more players to select because some U23 players did well at the AFC championship. This will help make the senior team stronger.”
Nishino, 64, guided Japan’s junior team to the 1996 Olympics and steered the country’s senior side to the last 16 round at the 2018 World Cup.