At 0311 GMT, IRPC shares were up 5.8 percent, while the overall Bangkok market was 0.24 percent higher.
The disputes included those related to feedstock contract with cement maker TPI Polene, also founded by Prachai, the company said in a statement.
IRPC, formerly known as Thai Petrochemical Industry (TPI), became Thailand's largest corporate debt defaulter after it collapsed under a mountain of foreign debt during the 1997/1998 Asian economic crisis.
The government of former prime minister Thaksin Shinawatra intervened in 2003 and state-run PTT PCL, Thailand's top energy firm, took control of TPI late 2005 as part of a restructuring.
The company completed its $2.7 billion debt restructuring in 2006 after numerous delays as Prachai waged a bitter campaign against the then government and TPI's many creditors.
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