A craze for lifelike dolls thought to bring good luck is sweeping Thailand, reflecting widespread anxiety as the economy struggles and political uncertainty persists nearly two years after a coup.

Thailand is predominantly Buddhist and has been modernizing rapidly over the past two or three decades but many people are highly superstitious, their Buddhist beliefs co-existing with notions of animism, astrology and "black magic".

The plastic dolls, about the size of a real baby, are called "look thep", or "child angel".

Devotees buy them in shops or online and invite benevolent spirits to possess them, hoping they will bring good luck.

"The economy is bad right now. Everybody needs something to hold on to," said Mananya Boonmee, 49, a doll owner and seller.

Mananya told Reuters her doll, called Nong Petch, or baby jewel, had helped her win the lottery by telling her what numbers to buy in her dreams.

Panpimon Wipulakorn, deputy director-general of the Department of Mental Health, said the economic downturn exacerbated the phenomenon.

"There have always been groups in Thai society that hold such beliefs and economic worries only help to heighten these beliefs," Panpimon told Reuters.

"These people do not have mental health problems."

Thailand has been ruled by a junta since a May 2014 coup and the generals have struggled to revive the export-dependent economy, while promising to restore democracy with an election next year.

Such fads have happened before. After a 2006 coup, many people turned to plasticine amulets, or charms, in the belief they would bring riches.

Devotees of the dolls lavish attention on them.

"My life has changed a lot, for the better," said beauty salon owner Natsuda Jantabtim, 45, who has had her doll - Nong Ruay Jung, or baby so rich, for eight months.

"When I hug her, I know it's love. I tell her I love her all the time."

Prime Minister Prayuth Chan-ocha weighed in on Monday saying people who could not afford to buy the dolls should not do so.

"I've never raised a child angel doll," he quipped.

The dolls cost from 1,500 baht ($40) to up to 30,000 baht ($800) and some businesses are tapping in on the craze.

Thai Smile, a subsidiary of national flag carrier Thai Airways, said it would charge passengers who bring dolls on board and would serve them snacks.

But the Civil Aviation Authority of Thailand said it would stop airlines selling tickets for dolls over concern they could be used to smuggle drugs.