Before the war began, Ms. Ruamthot, who has dished out som tum, or green papaya salad, for 20 years, would start receiving orders in person and on delivery apps before she had even finished setting up her stall in the morning. At lunchtime, she would serve a flood of customers, many of them office workers, who would wait up to 30 minutes.

These days, she does the waiting.

“It’s so bad now. Business is very slow,” said Ms. Ruamthot, 62.

Even though her costs have risen by about 30 percent, she has not increased her prices out of fear that doing so would drive more customers away.

“Even with the current price, we are losing customers,” she said. “People really live frugally because everything has increased in price.”

Her profits had fallen by more than half, to about 1,000 baht a day (around $30), leaving her unsure how long she could sustain her business. When she speaks with other food vendors, she learns that her situation isn’t unique.

“Everybody is experiencing the same thing,” she said.