Sanam Luang is often viewed as a large "home" for vagabonds, but few realise that many of the homeless who used to sleep there now rest with a roof over their heads in homes they have helped build.
Kai, a man who sheltered at the Phra Meru ground near the Grand Palace for 10 years, now has a house of his own in Phutthamonthon Sai 2 area in the western end of Bangkok, a way of life he had never dreamed would be possible.
Speaking with the Bangkok Post in a jubilant mood, the 51-year-old said he now sleeps more comfortably at night. He sleeps with a roof over his head, and no longer has to huddle under a plastic sheet in the rain or curl up in a phone booth to stay dry.
But what Mr Kai describes as ''a major life change'' comes with a cost. Unlike the food or other handouts which homeless people receive from donors, he has to pay for his new home, built under a joint project by the Human Settlement Foundation and the Ministry of Social Development and Human Security.
The project requires its beneficiaries to join the foundation's savings programme, which - instead of simply doling out state assistance as it might have done in the past - forces them to bear part of the responsibility for housing expenses.
Individual participants who want to live in houses in the new residential area - located by a railway track in Phutthamonthon Sai 2 and owned by the State Railway of Thailand - must save at least 400 baht per month. Families must save 700 baht.
This requirement is not too demanding, according to Mr Kai, who together with his wife, says they can afford it simply by cutting costs and taking on small jobs every day.
"Kind people are giving out food in many places," Mr Kai said, referring to The Old Siam shopping complex, Wat Phichai Yat and the National Council on Social Welfare, where portions of food given out to homeless people in the morning are enough to last the whole day.
As for Mr Kai's jobs, he said he does not have many choices because he dropped out of school after Prathom 2 (Grade 2) in his home province of Saraburi. His only experience is working with a rickshaw and in a fish sauce factory.
What he can do is to work small jobs on temporary hire, and collect used plastic bottles and paper for resale, he said.
He takes advantage of what he calls "money time" during festivals at Sanam Luang and some city streets, when there are multitudes of bottles to collect and, at the same time, he can sell sheets of plastic to revellers to sit on.
The most important thing is ethics, says Mr Kai, along with the social workers who have helped him.
"We have to stick to only honest jobs," said Uncle Dam, Mr Kai's friend and an adviser at Suwit Watnoo homeless centre near Charan Sanitwong railway station in Bangkok Noi district.
The centre, named after the late social advocate Suwit Watnoo, houses 40 families which once included Mr Kai and his wife.
The couple's new house is part of a housing village in Phutthamonthon Sai 2 which can accommodate up to 28 people.
The Social Development and Human Security Ministry also runs another homeless centre in Chiang Mai to build long-term housing security for people upcountry, said minister Pol Gen Adul Sangsingkeo.
He stressed the importance of poor people learning to save money, and obtaining an income through honest means.
If they were able to help themselves in this way, their status as homeless people would soon be a thing of the past, he said.
Mr Kai's new house in Phutthamonthon Sai 2 is number 001.
It is nothing special, except that it will always be a reminder of one key moment in his life — the time when he stopped wandering and started living.