The debentures, with 3.70 per cent annual return, was rated BBB by Tris Rating.
It will be available for subscription to the public from February 11-13 via Krungthai Bank.
Interest will be paid quarterly. Minimum investment is Bt100,000.
The key purpose of the issuance is to raise funds for the construction of the SRT Light Red Line Project in the suburban area of Bang Sue-Rangsit and other future projects.
The company appointed Krungthai Bank to be the underwriter of the Bt3-billion debentures, Unique senior vice president of accounts and finance Toemphong Mohsuwa said.
Unique is poised for growth from the much-anticipated public transportation infrastructure projects in the years ahead, the statement added.