His death comes days after China announced that it had temporarily banned exports by the company.
Lee Der made 967,000 toys that were recalled earlier this month by US-based toy giant Mattel because they were made with paint containing excessive amounts of lead.
The plastic pre-school toys, sold under the Fisher-Price brand in the US, included Big Bird, Elmo, Dora and Diego characters.
The Southern Metropolis newspaper said that a supplier, said to be Zhang's best friend, had sold Lee Der the paint that was used in the toys.
Liu, a manager of the company was quoted as saying: "The boss and the company were harmed by the paint supplier, the closest friend of our boss."'
Liu said Zhang hanged himself on Saturday.
No other details of his death were reported, but police were said to be investigating.