Kiatisak Senamuang has agreed to coach the full national side with his first assignment being next month's Suzuki Cup.
Kiatisak Senamuang at the Asian Games in Incheon, South Korea. Pattarapong Chatpattarasill
Affectionately called 'Zico', the former Thailand striker guided the national U23 side to win the SEA Games gold medal last year and reach the semi-finals at the recent Asian Games.
During the Asian Games in Incheon, South Korea, Kiatisak repeatedly said he would not accept the national team coaching job as he wanted to take a break.
But Worawi Makudi, president of the Football Association of Thailand (FAT), announced on Monday Kiatisak had agreed to take the position.
"After talks, Kiatisak agreed to coach the national team as well as the U23 side," Worawi said.
"We will allow him to choose his staff and his first task will be next month's Suzuki Cup [Southeast Asian championship]. Our target is to win the Suzuki Cup."
Worawi added: "Players from the Asian Games team will be core members of the Suzuki Cup squad and also the team for the 2018 World Cup qualifying round."
He said Kiatisak would receive a formal contract next week.
Kiatisak said he decided to coach the national team after talks with FAT officials and senior people in the country's footballing circles.
"I will start my job immediately as it is important to win back the Suzuki Cup," said Kiatisak.
Thailand have not won the biennial tournament since their last triumph in 2002.
Thai U19 team advances
Thailand reached the quarter-finals of the AFC U19 Championship after beating Yemen 3-2 in their last Group A match in Myanmar last night.
In the other Group A game, Iran beat Myanmar 3-2.
Thailand and Myanmar advance to the quarter-finals. The top-four teams of the tournament earn berths for next year's U20 World Cup in New Zealand.
Thailand hope to see another squad seal a World Cup berth after the women's side secured next year's World Cup spot.