Witawat, 44, who was replaced in June as Ogilvy & Mather Advertising managing director in Thailand by another long-serving O&M staffer Punnee Chaiyakul following a management reshuffle, will team up with TBWA, which is buying local advertising agency Creative Juice.
Witawat, who was with O&M for 13 years, will head the new joint-venture agency, which has yet to be named.
The deal is expected to be finalised by the end of September and is being financed by TBWA at a cost of 40 million baht (US$950,000).
"TBWA will provide the financial support and a substantial client base to begin with, said Witawat, who is in his last month at O&M.
Several former senior O&M Thailand staffers, including ex-client service director Songkran Sethsompob, will join Witawat. Songkran left the company in August, about the same time Witawat announced his resignation.
"They all left the company before I did and went to other companies, he said. "When they found out I was starting a new company they decided to join me. It's like a reunion."
O&M has moved swiftly to ensure Witawat - the group's chief strategist - does not leave with any accounts.
"From our side, we'll be doing our best to keep our existing accounts by continuing to create a feeling of trust, said Ogilvy Group Thailand vice-chairman, Chutharat Thanapaisarnkit.
Witawat said TBWA approached him with the merger idea two months ago.
He insisted Creative Juice's 30 staff would keep their jobs, and that another 20 positions would be created. Creative Juice recently snared the three-year Thai Airways domestic account. It also has the Tourism Authority of Thailand as a client.
Witawat said TBWA would bring with it a number of local and international clients, but he would only reveal Chivas Regal among them.
