This story is part of Forbes’ coverage of Thailand’s Richest 2025. See the full list here.

Four years after diversifying into telecoms, energy tycoon Sarath Ratanavadi is reaping the fruits of that strategic move. In April, he concluded the merger between his power producer Gulf Energy Development and Intouch Holdings, the biggest shareholder in Advanced Info Service (AIS), the country’s second-largest mobile phone operator by subscribers, with the listing of the rebranded Gulf Development on the Thai stock exchange. Its market cap of 640 billion baht ($20 billion), makes it Thailand’s fourth most valuable listed company.

The tycoon’s net worth zoomed 30% to a record $12 billion and he jumped two places to become the country’s third-richest for the first time. Sarath, who founded Gulf in 2007, continues to eye new ventures.

Last year, the company joined with Google Cloud to build AI-powered cloud facilities in Thailand while its joint venture with Binance, cofounded by Changpeng Zhao, launched a Thai edition of the cryptocurrency exchange. Gulf has also acquired a roughly 5% stake in Kasikornbank, founded by fellow rich lister Banthoon Lamsam’s family. Notably, AIS is part of a consortium that secured approval in June to set up a virtual bank.