A Thai diving instructor is struggling to save one of Bangkok's oldest homes amid the relentless demolition of historic buildings in the rapidly modernising city.

Poosak Posayachinda, 57, inherited the crumbling 200-year-old Chinese mansion - a piece of architectural heritage - from his family in 2004 but its operating and maintenance cost a fortune.

To have money for the enormous 30-room house's upkeep, the teacher built a pool in its garden where there used to be patches of beautiful roses and an apple tree once stood so he could start his own scuba diving school.

His school's unusual location has attracted students and curious visitors who take selfies in the grounds, saving his piece of cultural gem that is almost without any protection under Thai laws, which show little respect for historical buildings in the face of developers buying up land.

Teacher Poosak, whose ancestors moved from China to the emerging city of Bangkok, said: ‘This house is an ancient Chinese home and I believe it is the oldest that is privately-owned in the city.

‘It was built by an ancient Chinese constructor. It has a Chinese Hokkien architecture style that has a garden in the middle and the house surrounds the pool in four directions. In the middle, it used to be a multipurpose area.

‘When I was just born it was a rose apple garden and it started to become dirty, with nobody to take care.'

The diving teacher added that around the time he was starting to put up his business, the mansion started to break so he was pushed to do something about it.

He said: ‘Especially the wood, it started to break and the color started to fade and I thought I had to do something to the house.

‘It happened to be at the same time I was doing the diving business so I put a pool here. As the pool was being installed, we then have the house renovated too.'

Poosak used his own money for the renovations and gradually earned profits from its new purpose.

He said: ‘I spent it all from my wallet. My students come here and take pictures, take selfies and post it on Instagram and Facebook so people started to come to a look.

‘It first started with only one or two people then there were ten people a day and then strangers just open the door and enter .

‘If nobody was willing to look after it then I will. So many people come so then I came up with a ticket entry system.'

Poosak eventually let go of the ticketing scheme and sold coffee to visitors instead.

The teacher added': And then I thought it was too forcing, so I switched to selling coffee. So it gave an understanding that if you want to come inside, each person has to order at least a drink and I can choose who to enter my house.

‘So if I find a group of customers that is loud and noisy, I can choose to not serve them. Because it is my right.

Despite earning some money from the small business he built around the mansion, the diving instructor is still drowning in maintenance bills.

He said:'I use the cafe's money to take care of the house maintenance but it's still not enough to fix and maintain its original shape.'

But despite everything, Poosak wouldn't sell. He explained: ‘I received many buying offers for this house, but I don't sell. Regardless of the number they value this house, I will not sell it.

‘First reason is, that the people who built this house did not do it just so I can sell it, they built it for their descendants and I am one of them. And the second reason is, that the builder wanted to pass it on to future generations.

‘So my children or my grandchildren can live in this house. Now some parts are closed and I think I might consider permanently closing this place.

‘I don't care. I want to teach diving. For people who really want to enter this place, it will have to be a very special occasion to open.'

Now he is urging the people, especially tourists to respect these valuable structures so they mights survive for the next generation.

He said: ‘In the past there have been foreigners getting on this property, I have no clue what are they looking for. They sat in this very place and started making out in the bright afternoon.

‘I felt like what they were doing was not right in a public space. So I'm considering shutting this place down.

‘If I can fix it I will, but if it can't be fixed then let it break. I don't know what to do too.'

The Mansion, So Heng Tai, has stood in Bangkok 's China town since King Rama I from the 1782 A.D. It also is the oldest Chinese Court Yard mansion the Southeast Asian country.