Prices of chicken eggs shot up by five to six baht per tray of 30 on Monday, with the Layer Chickens Association attributing the increase to the high cost of feed and farm drugs.
Association president Manote Chuthapthim said egg prices had risen from 2.80 baht apiece to three baht because farmers could no longer carry the increasing costs.
The cost of feed was not expected to fall in the foreseeable future.
Even so, ex-farm prices of eggs in mixed sizes must not exceed 3.44 baht apiece, as the Egg Board had set the mark-up ceiling at no more than 20% of cost, Mr Manote said.
Prices would eventually decrease during the school term break and the annual vegetarian festival, he said, but did not explain why. Nor did he explain farm drug costs.
The country currently has about 50 million laying hens that produce around 40 million eggs a day, most for the domestic market, according to the association.
In Nakhon Sawan province on Monday, eggs had risen by 20 satang each, or six baht a tray.
Sangwian Maidaeng, a restaurant owner, said pork had risen to 240 to 250 baht a kilogramme last week, but he did not want to raise prices. Now, with the increase in egg prices on Monday morning, he had no choice but to pass on the added cost.
"I can't keep prices unchanged because I can't carry the higher operating costs. I'm not even sure if I can continue running the restaurant because higher prices may result in fewer customers," Mr Sangwian said.
At a wet market in Khon Kaen province, size 0 eggs were being sold at 120 baht a tray, with smaller sizes ranging from 105 to 80 baht a tray.
Jetsada Champanui, an egg vendor, said customers were the ones suffering because they also had to cope with the higher price of pork.
"I believe egg prices could go up still further, because a tray of eggs increased by 10 baht in August last year.
"The government should fix the price at three baht a piece," Mr Jetsada said.