BANGKOK (REUTERS) - Thailand's king now has a stake worth nearly US$150 million (S$197 million) in the country's biggest industrial conglomerate, Siam Cement Group Pcl, according to stock exchange data, while his close aide is in line for a board seat.

Since taking the throne in 2016, King Maha Vajiralongkorn has brought management of the monarchy's multi-billion dollar holdings under greater personal control and last year also took a US$500 million stake in Thailand's oldest bank.

The 0.76 percent stake in the king's name in Siam Cement was acquired on Feb. 8 while there was a matching reduction in the stake of the Crown Property Bureau, which manages palace assets, according to data from Thomson Reuters Eikon.

This follows a similar transfer of shares - now worth nearly US$540 million - in Siam Commercial Bank Pcl from the Crown Property Bureau to the king last year.

The terms of the transfers have not been disclosed in public. Neither company nor the Crown Property Bureau would comment on them.

The palace has a policy of not commenting to media.

At the most recent rates, the dividend yield from the king's holdings in the two companies would be more than US$25 million per year.

The Crown Property Bureau's holding in Siam Cement is now 30 percent. It remains the biggest shareholder.

The king is listed by the stock exchange as the 15th largest shareholder in Siam Cement and the sixth biggest in Siam Commercial Bank, Thailand's second largest by assets.

Siam Cement said that Air Chief Marshal Satitpong Sukvimol, a close aide to the king who was made director general of the Crown Property Bureau this month, had been recommended for a board seat at a March 28 annual general meeting.

Kasem Wattanachai, another member of the Privy Council which advises the king, has also been nominated for a board seat by Siam Cement's Governance and Nomination Committee, according to a note to shareholders ahead of the meeting.

Satitpong had long served as private secretary to King Vajiralongkorn before he ascended the throne following the death of his father, King Bhumibol Adulyadej.

The exact size of the Crown Property Bureau is not made public, but recent estimates have run to more than US$30 billion through its holdings in real estate and other investments.

Rich-list publisher Forbes once described the former king as the world's richest royal, but was rebuked by the Thai embassy in Washington, which said assets in the Crown Property Bureau were not his property but held "in trust for the nation".

Few in Thailand comment on anything related to the monarchy given a law setting a sentence of up to 15 years for saying anything deemed offensive.