Irregularities during Thai stocks plunge -finmin

BANGKOK, Oct 22 (Reuters) - Thailand has detected trading irregularities on two stock trading accounts when there was a big sell-off in Thai shares last week, Finance Minister Korn Chatikavanij said on Thursday.

The sell-off by local institutional and foreign investors caused a combined 7.2 percent plunge in stock prices on Oct. 14 and 15, wiping out 427 billion baht ($12.8 billion) of market value.

Korn told reporters the accounts in question were based overseas but it was not clear who owned them.

"We will seek cooperation with the stock exchange of Thailand and overseas bourses because we have found that there were two accounts which saw unusual movements before the market rumours," he said.

Separately, Thirachai Phuvanatnaranubala, secretary general of the Securities and Exchange Commission, told reporters the SEC was seeking trading information on the two accounts from two foreign brokers, Credit Suisse in Hong Kong and UBS in Singapore.

The SEC was also inspecting one domestic stock trading account, looking for possible irregularities, he added.

On Friday the government and the SEC announced plans to take legal action against people found responsible for rumours related to the health of Thailand's king that triggered the plunge in stocks.

King Bhumibol Adulyadej, 81, the world's longest reigning monarch, has been treated at Bangkok's Siriraj Hospital since Sept. 19 for fever, lung infection and loss of appetite. [ID:nBKK397878]

The health of King Bhumibol is an extremely sensitive topic in financial markets. He is seen as the single unifying figure in a politically polarised country with a long history of military coups and upheaval. ($1=33.44 Baht) (Reporting by Kitiphong Thaicharoen; Writing by Viparat Jantraprap; Editing by Alan Raybould)