Bangkok | A Japanese tourist reaches into a baggie of cannabis he's just bought in a central Bangkok weed shop, pulling out a gram of buds to chop down in a small black grinder, before rolling them neatly into a joint.

Only the slight spillage onto the smoking lounge's table — and his cough as he lights up and inhales deeply — betray the fact that until two weeks ago, he'd never tried marijuana.

Most Asian nations have strict drug laws with harsh penalties, and Thailand's de facto legalisation of marijuana last year has brought a wave of tourists from the region like the visitor from Japan, intrigued by the lure of the forbidden leaf.

“I was curious about how I would feel after smoking,” said the 42-year-old tourist who spoke on condition that his name not be used, for fear his experimentation in Bangkok could lead to legal issues at home.

“I wonder why Japan bans it?" he pondered. "I wanted to try it.” Even as more countries around the world legalise marijuana, Thailand has been the outlier in Asia, where several countries still have the death penalty for some cannabis offenses.

Singapore has already executed two people this year for trafficking marijuana and its Central Narcotics Bureau has announced plans to randomly test people returning from Thailand.

Japan does not have the death penalty for drug offenses, but has warned that its laws on cannabis use may apply to its nationals even when they are abroad.

China has been more explicit, with its embassy in Thailand warning that if Chinese tourists consume marijuana abroad and are “detected upon returning to China, it is considered equivalent to using drugs domestically.

As a result, you will be subject to corresponding legal penalties.” It issues similar warnings for travel to other countries where marijuana is readily available, such as the United States, Canada and the Netherlands.

On a recent flight from the Chinese city of Shanghai, passengers were cautioned not to “accidentally” try marijuana in Bangkok, with an announcement that in Thailand “some food and drink can include cannabis, so please pay attention to the leaf logo on the package of food.” Neither Chinese nor Singaporean authorities would detail how frequently they tests citizens returning from countries where marijuana has been decriminalised, responding to queries from the AP simply by reiterating their previously-announced policies.

It's no wonder that weed dispensaries in Bangkok say that customers from Singapore and China are among the most cautious, asking questions about how long traces of the drug remain in the system and whether there are detox products.

But many remain undeterred, and Thailand's cannabis industry has grown at lightning speed, with weed dispensaries now almost as common as the ubiquitous convenience stores in some parts of the capital.

Through February, nearly 6,000 licenses for cannabis-related businesses have been approved, including more than 1,600 in Bangkok alone, according to official figures.

There are no government figures on how many tourists come specifically to smoke marijuana, but Kueakarun Thongwilai, the manager of a weed shop in central Bangkok, estimates at least 70 per cent-80 per cent of his customers are foreigners, primarily from Asian countries like Japan, Malaysia, China and the Philippines, and some from Europe.

Most cannabis shops, including his, now only hire employees who speak English, the lingua franca of the industry.

“You don't need to speak perfect English, but you need to communicate with foreigners,” Thongwilai said.

About half of his customers are first-time weed users and most of them are Asians, he said.

Some want to try edible cannabis products, but Thongwilai said he tries to steer them toward smoking.

“Edibles take more time to take effect, and during that time people may eat more and more, leading to an excessive experience for beginners,” he said.

Not all are new to the drug, said Thongwilai, remembering a Malaysian customer who snuck away from a meal with his wife and daughter at a nearby restaurant. The man said he smoked marijuana secretly at home, but had heard the Thai product was better quality and wanted to try it.

“He bought the cheapest weed in our shop and tried it in a mall, and then he came back and bought more,” Thongwilai recalled.

Not far from Thongwilai's shop at Dutch Passion, a newly opened retail branch of a Netherlands seed distributor that has been in business for more than three decades, about half the customers are also first-time users, said Theo Geene, a Dutch shareholder in the business.

Cannabis has been available in coffee shops in the Netherlands since the 1970s, and Geene said he has used his experience to train his staff how to serve those unfamiliar with the drug.

“For beginners, it's not good to use a bong,” he said. “It's too much for them. We don't want anyone to pass out here.” Most customers refused to talk about their experiences, with the Japanese tourist in Geene's shop the only one who agreed to — and only on the condition his name not be used.

Most of the shop's Asian customers are similarly discreet, choosing to smoke their purchases inside rather than on the streets like many Westerners do, which is common but a violation of Thai regulations, Geene said.

“They are more cautious and afraid,” he said. “They don't want to be seen when they smoke weed.” Before he embarked on his trip to Thailand, the 42-year-old Japanese tourist said he researched extensively online and determined that while customs might randomly check bags and luggage for marijuana being smuggled into Japan, there was no testing going on in line with government policy.

Since his first puff two weeks ago, he said he's been smoking every day, visiting different shops, comparing prices and trying different strains.

Dispensary staffers taught him how to grind buds and roll a joint and he's been having fun perfecting the technique.

“I practice it every day,” he said, looking down at the joint he was rolling and repeating the word “practice” twice before bursting into laughter.