Intouch owns stakes in Thailand's largest mobile phone network Advanced Info Service Pcl and satellite operator Thaicom Pcl.
The deal, Southeast Asia's largest block trade in 2019, sent Intouch shares down nearly 6% on Thursday in Bangkok trading.
Intouch shares, however, gained 27% year-to-date against a benchmark rise of 3.55% <.SETI>; stock was priced at 60.75 baht on Thursday at a pre-close of 64.5 baht.
Intouch did not immediately respond to a Reuters request for comment.
Former Prime Minister Thaksin Shinawatra sold InTouch, then known as Shin Corp, to Temasek in 2006, setting off public criticism that led to his ousting in a coup.
Singapore Telecommunications Ltd currently owns 21% of InTouch.
Credit Suisse was one of the book-runners.
(Reporting by Anshuman Daga in Singapore and Chayut Setboonsarng in Bangkok, Editing by Sherry Jacob-Phillips)