By Ju-min Park and Heekyong Yang

SEOUL (Reuters) - A South Korean court ruled SK Group Chairman Chey Tae-won must pay more than $1 billion to his estranged wife as part of their planned divorce, sending shares in the group's holding firm surging on speculation that he will have to purchase more stock to cement his control.

The Seoul High Court found Chey's shares in holding company SK Inc should be counted as part of the couple's joint property, overturning a 2022 ruling by a lower court for a much smaller amount.

Chey was ordered on Thursday to pay 1.38 trillion won ($1 billion) in cash and 2 billion won in alimony to Roh Soh-yeong, the daughter of former South Korean President Roh Tae-woo.

Chey's lawyers said he will appeal.

Shares in SK Inc jumped 9% after the ruling, giving it a market value of some 2 trillion won.

Chey owns 17.7% of the SK Inc and controls SK Hynix, the world's second-largest memory chip maker, and other SK affiliates through his stake in SK Inc.

Park Ju-gun, head of corporate analysis firm Leaders Index, said that since the court ruling did not stipulate that Chey split his stock holding with Roh, he thought the chances of increased purchases of SK Inc stock were low.

He also said that, assuming the ruling stands, he thought Chey would be unlikely to sell his shares to make the payment but would probably take out loans using his SK Inc stock as collateral.

SK Group is South Korea's second-largest conglomerate in terms of assets after Samsung, according to the country's Fair Trade Commission.

($1 = 1,378.59 won)