The agency, which was formed in 1978, has 70 employees and billings estimated at $30 million.
The deal gives Thomas 49 employees and billings estimated at more than $50 million.
Addison Whitney has 19 employees and billings estimated at $6 million.
Technology Solutions has 135 employees and billings estimated at $14 million.
The combined agency would be San Francisco's 12th-largest, with 50 employees and billings estimated at $48 million.
Laird opens with 20 employees and billings estimated at $120 million from the two clients.
The agency opens with 15 employees and fees estimated at more than $3 million from 19 clients including the Time Inc.
Warner, Bicking has 10 employees and billings estimated at $10 million.
That office has 110 employees and billings estimated at $100 million.
The merged agency will have 51 employees and billings estimated at $60 million.