The group said the two- and three-digit lotteries had affected them badly, but the vending scheme would cut their chance of making a living to near zero.

They also claimed that many firms bidding for the machines had ties to ousted premier Thaksin Shinawatra.

The group, led by Thailand Association of the Blind adviser Somchai Panyaekwong, called on Prem to also halt the plan to import vendors by a major business conglomerate.

An aide of Prem who received the letter said that he would pass it on to Prime Minister Surayud Chulanont.

Meanwhile, Deputy police chief Pol Lt-General Jongrak Juthanont predicted that betting on the underground lottery would become rampant during the absence of government lottery operations in December.

He said all police stations had been told to act against underground bookmakers and complete investigative reports and file indictment to the courts in cases of bets higher than Bt200,000.

Deputy Democrat spokesman Aphichart Sakdi-seth called on the government to withdraw the bill aimed at legitimising the two- and three-digit lotteries and reconsider the conditions before submitting the draft to the National Legislative Assembly.