BANGKOK, Thailand (AP) _ An investor who went bankrupt playing the stock market shot himself in the lobby of the exchange building today. ``My blood will help clean the stock market,'' he said after an operation to remove a bullet from his neck.

Vivat Srisammasheap, 49, took his gun and sat on the floor of the Stock Exchange of Thailand, demanding to speak to exchange president Seri Chintanaseri.

An exchange official tried to calm Vivat, speaking to him through a bullhorn from a balcony, as Seri made his way to the lobby. ``But he didn't wait,'' said Suvicha Mingkwan, a spokesman for the exchange.

``He told police he was broke and had gone bankrupt,'' Suvicha said, adding he had heard that Vivat had lost between $1.2 million and $1.8 million.

About 70 or 80 investors, including Vivat, had protested outside Seri's office today, demanding the top exchange officials resign and that rules be changed to help boost the sagging SET index.

The index has plummeted to its lowest level in almost six months. Analysts and exchange officials attribute falling stock prices to tight monetary policies, high interest rates and investors' lack of confidence in the current government.

Vivat stayed behind in the lobby, pulled out his gun and began making demands.

``I won't die so easily,'' Vivat told reporters in the hospital after undergoing surgery.