As the boycott was spreading in the northeast, mostly through social media and word of mouth, Ms. Chitpas wrote on her Facebook page that she was fighting for the country and had no intention to “infringe” on other people’s rights. She did not deny the words attributed to her about Thais lacking an understanding of democracy, but she added, “I would like to inform you that I’ve never looked down on rural people at all.”

She did not respond to a request for further clarification.

Kwanchai Praipana, the head in the northeast of a group of so-called red shirts that supports the government, says the point of the beer boycott is to send a message to companies with links to the protesters: rural people vote in elections — and with their wallets.

“We want to tell the businessmen who are supporting these protesters that they have chosen the wrong side,” Mr. Kwanchai said. “They have to understand that their revenue comes from villagers.”

Boon Rawd Brewery, the company that makes Singha and Leo, a cheaper beer that is popular in the northeast, declined to reveal the extent of the damage caused by the boycott. But some shopkeepers say sales of Singha and Leo around New Year’s, traditionally a time of heavy drinking, were down sharply.

Kittisak Srichan, the owner of Khrua Khun Nit, one of the most famous restaurants here, said he removed Singha beer and Singha bottled water from the dining area last month. “I don’t want to anger the customers,” Mr. Kittisak said. “Customers said to me, ‘Why are you selling this? The only thing this beer should be used for is pouring on your feet.’ ”

Facebook pages have been filled with images of just that: bottles of Singha and Leo being poured onto feet — a disparaging gesture in Thailand.

Ms. Chitpas — who ran unsuccessfully for Parliament in 2011 — and other protest leaders argue that Thailand’s democracy has been subverted by the governing party, especially the powerful Shinawatra family that has dominated Thai politics for the last decade. They remain unsatisfied by Ms. Yingluck’s decision to call new elections after the protests began — elections analysts say the governing party is almost sure to win.