It's a sweaty Saturday morning in Bangkok, and while most 12-year-olds are winding down for the year, Ralyn Satidtanasan — or Lilly as she's called — is getting ready to scoop plastic out of a canal.

"There's so much single-use plastic in this canal alone, imagine how much there is in the ocean," she tells the ABC on a boat in a canal in north-west Bangkok.

"It's extremely shocking because if you think about it, this is just not even 1 per cent of what we're seeing in the oceans today."

Lilly is a regular at weekly Bangkok events organised by Trash Hero — a volunteer group that picks up rubbish at dozens of locations around the world.

The Trash Heroes hold weekly events in Bangkok and pick up rubbish in 12 different countries. ( ABC News: Amy Bainbridge )

But it is Lilly's work fronting up to retailers and the government, asking them to rethink their policies on single-use plastic, that has seen her dubbed the Greta Thunberg of Asia.

From January 1 single-use plastic bags will be banned in major stores in Bangkok.

Lilly has been meeting directly with retail executives and government officials to drive the policy.

"I've been working with the Ministry of Natural Resources and 43 major companies that are trying to reduce and ban single-use plastic bags in their stores by next year," she says.

"We're trying to push it even more for every company and every shop in Thailand to not use any single-use plastics at all."

There was plenty of resistance in Australia when a ban on single-use plastic bags was introduced by major supermarkets in 2018.

Lilly's journey hasn't been an easy one either.

'They tell me that I can't do it'

Lilly says some people have found it hard to take her seriously. ( ABC News: Amy Bainbridge )

A beach visit as an eight-year-old opened Lilly's eyes to plastic pollution, and with the support of her two environmentally aware parents, she began meeting with anyone who would talk to her.

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She readily admits it is hard to be taken seriously by some people.

"Yes, there are really big struggles and people who don't really trust me or believe me.

"Or they try not to talk to me as much and there is some resistance as well."

She has told many people the same thing: it's time to act.

"We really need to act now because of how big this issue is really becoming," she says.

"I can't walk on the street right now without finding a piece of single-use plastic, and honestly that isn't something positive.

"They always tell me that I can't do it, or this is such a big problem that I shouldn't be worrying about it and that I shouldn't be the one telling these big companies and the government to stop."

Lilly says she looks up to Greta Thunberg.

"She’s a huge idol for kids around the world. She does help us with trying to feel more confident in doing these things, because if you really think about it, she teaches us that we are not too small to make a big change.

"She really teaches us that we can make a difference, no matter how small we are."

Bag ban could cut plastic problem in half

Plastic pollution is a big problem in Thailand. Here, people are shovelling it out of a canal. ( ABC News: Amy Bainbridge )

Thailand has a population of 70 million and environmental scientists say plastic pollution is a big problem.

Plastic is making its way from Bangkok's canals to the ocean, and ending up in sea life and other animals.

Stefanos Fotiou from the United Nations Economic and Social Commission for Asia and the Pacific says most of the plastic in Thailand is not being recycled.

Stefanos Fotiou says the majority of Thailand's plastic is not being recycled. ( ABC News: Amy Bainbridge )

In December, when the ABC caught up with him at his office, he was taking a brief break from chairing a meeting of ASEAN nations to discuss natural resources issues.

At the meeting, plastic waste was the number one concern.

"A representative of Thailand told us that the latest figure is that there are 2 million tonnes of plastic waste every year, that's municipal plastic waste," he explained.

"And out of this 2 million tonnes, 1.2 million tonnes is plastic bags.

"And of that 2 million tonnes, only a quarter is properly re-used and recycled and the rest is ending up in the sea."

He said the plastic bag ban would make a big difference if it was properly enforced and implemented.

"If we know that 60 per cent of the plastic waste is plastic bags, if it's properly imposed … then the ban could solve 60 per cent of the problem. This is a big step.

"It's necessary I would say but not sufficient. We need to see the entire cycle of plastic production and how many single-use plastics could be substituted by other material.

"I think no country has a choice, all of the countries should take very drastic measures."

'We are eating it'

One of the biggest concerns about plastic pollution is the impact it has on human health. ( ABC News: Amy Bainbridge )

One of the biggest concerns — but one that Dr Fotiou says few people are aware of — is the impact of plastic on human health.

"At one point we were thinking it's only bad for diversity and the natural environment, but now all of this plastic goes back to the people — it goes to the food stream, and we are eating it," he said.

"All species that are in the sea are affected by the plastic bag. Fishes, whales, we have seen how many plastic bags they are eating.

"This plastic starts to disintegrate, and it becomes what we call microplastic, very tiny parts of plastics that we cannot really see. But they are eaten by the fish and it goes into the bloodstream, it goes into the protein.

"We are eating it when we eat the fish and microplastics have now been identified in the human bloodstream.

"So we are eating microplastics every day when we eat food."

Thailand produces an estimated 2 million tonnes of plastic waste every year. ( ABC News: Amy Bainbridge )

For him, young people like Lilly are an important way to get the world to listen about environmental problems.

"She's a big advocate to the youth, which are the ones who can change the behaviour.

"She's demonstrating how you walk the talk of sustainability.

"And because she has become quite a public figure, she has the ability to talk to policymakers, she has the ability to talk to influential people and make them look at things from another perspective.

"I think that Lilly and all the youth that are involved in the environment and climate movement are bringing a fresh breath to the environmental movement because some feel a little different when a 12-year-old highlights a problem."

Lilly and her parents at a Trash Heroes gathering in Bangkok. ( ABC News: Amy Bainbridge )

Consumers divided

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Nowhere is single-use plastic more prevalent than in Thailand's 7-Eleven stores.

There are 10,000 branches across Thailand, and plastic has become the ultimate convenience in the form of spoons, straws and small bags to put items in.

Even fruit like bananas are sold individually in clear plastic.

One man in his 50s who was shopping at a 7-Eleven store told the ABC the bag ban would be inconvenient.

"It is difficult to have a cloth bag (with us) unless we plan before we buy things," he said.

"If we buy a lot of things it will be difficult.

It's better if customers can choose."

But another customer the ABC spoke to was supportive of the plastic bag ban.

"I think it is OK because reducing plastic use is also reducing world pollution."

Bag manufacturer seizes opportunity

Pasin Lathouras from the Naraya Group, a well-known Thai bag manufacturer, sensed an opportunity and has partnered with 7-Eleven to sell reusable cotton bags in the convenience stores.

Pasin Lathouras has partnered with 7-Eleven to sell reusable bags. ( ABC News: Amy Bainbridge )

"I think the opportunity is there, it's a very big change so we'll see how it rolls out through the year," he said.

He admitted it was a big undertaking for his brand to supply enough reusable bags to be sold when the ban comes in.

"All of our products are still handmade, so we'll have to see how we go with the sales and huge demand next year."

But he said he thought it would take some time for consumers to adjust to the new rules.

"It depends on the approach of different shopping malls and convenience stores. If they charge for some plastic bags then people are going to have a reaction.

"[They'd] maybe give a second thought to reducing their purchasing of the goods or reducing the quantities so they don't have to carry too much or pay for a second bag to carry their shopping."

"It's going to be a big change next year, for the whole country."