City boss Sven-Goran Eriksson, who took the helm after Thaksin bought the club in July, is due to arrive in Thailand on Friday to make the signings, said Vittaya Khunpleum, chairman of Thai side Chonburi FC.
Two of the players -- Suree Sukha and Kietprawut Sai-aeo -- come from his club, while the other player is Theerasil Daengda from Bangkok's Muangthong-Nongchok United FC, Vittaya said.
He said the chairman of the Football Association of Thailand told him about Eriksson's visit and the signings, and hailed it as a chance to showcase Asian and Thai football.
"Our players are qualified. If they can play in the (Man City) first team, football will become more interesting and it will help professional football in Thailand," Vittaya said.
"It is lucky that the chairman of the club is Thai," he added.