In a regulatory filing, the firm said its board has approved the proposal from the Thailand-based firm.
"The board considered and accepted the proposal from GP Group, Thailand, to invest in the company's Civil EPC business by investing in the company's wholly-owned subsidiary GRIPL," the filing added.
The board also approved draft of investor-cum-shareholder agreement among Gammon India, GRIPL and the GP Group, it added.
"GP Group shall invest a sum of Rs 250 crore, of which Rs 26 crore will be invested on consummation of Business Transfer Agreement (BTA executed on February 12, 2016 between the company and GP Group," it said.
GP Group will reconstitute the board of GRIPL to control the composition, the filing said.
GP Group's interests lie in construction, logistics, aviation, energy supply, pharma mining and the like.