Bright red numerals are beaming from a digital clock on the wall, silently counting each minute in the early morning. No one is awake yet. The janitors have not begun work.
There is only the faint sound of someone walking in the dim and stuffy hall. Slow at first, with small and halting steps, towards the light shining through the glass panes.
The champion is walking to work.
Ratchanok Intanon knows this routine by heart; her days have started this way since she was six.
She knows this place even better; it is where she has been nurtured from infancy after her family arrived from the north-east province of Yasothon.
Long before she became the toast of the Banthongyord Badminton School, and her name represented the best of Thai sport, she was just the daughter of labourers who made thong yord (a traditional Thai dessert of egg yolk and sugar) for a living in a factory a stone's throw away.
TALE OF THE TAPE
CAREER-HIGH WORLD RANKING
YOUNGEST WORLD CHAMPION (2013)
It's not just others who have high hopes, I'm expecting something from myself too. I'm not afraid to say I want to win a medal because I'm confident that I can really do it.
The self-proclaimed tomboy played shooting games with boys on the factory grounds, but was also admittedly quite the cry-baby.
"I'd open the window from the second floor and hear her cries from below," recalled Xie Zhihua, who has been coaching at Banthongyord since moving from China in 1992.
Little Ratchanok slept on a mattress on the factory floor while her parents worked with scalding sugar around her, until factory owner Kamala Thongkorn scooped the toddler away from danger - and put her on the same court, where Xie was employed to train her own three children.
There was little indication that badminton would be anything more than an activity to keep this child occupied. Said Ratchanok's mother, Kumpan Suvarsara: "She never showed any signs of becoming a great athlete. She was laidback, small and thin."
Kumpan reckons that what their family lacked in material belongings has in turn gained her child an invaluable life lesson.
When Ratchanok was about 10, she asked for a mobile phone.
"At that time, she was surrounded by friends who mostly came from rich families," said Kumpan. "I told her we couldn't afford it, and that if she wanted something, she's going to have to earn it herself."
Ratchanok understood that if she won enough games, she could take home more than a trophy.
So she endured it all. The 5.30am training before school. Two more sessions after classes. Step off a plane from competitions overseas only to be taken straight back to court. Training until you cried.
From the moment she clinched the national nine-and-under title as a seven-year-old, the narrative of her career has been one of winning when no one expected her to. It was apparent in the three straight world junior titles (2009-11), and again in her sensational 2013 upset of China's then-world No. 1 and Olympic champion Li Xuerui to become the youngest world champion.
NO WEIGHT'S TOO HEAVY
It would be too much burden for a normal 21-year-old, but not me. I'm strong enough to shoulder the expectations.
RATCHANOK INTANON, on how her tough beginnings have made her the person she is.
Everything has changed for Ratchanok. Yet very little has become different.
Now a member of world badminton's elite, she is also Thailand's first world No. 1 in any sport, reaching the coveted ranking in April (she is now ranked No. 4).
Lucrative endorsement deals from telcos and beverage companies have come knocking, her toothy smile fitted in braces is plastered on billboards across Bangkok, and there is no escaping requests for photographs and autographs wherever she goes.
But the pride of Thailand has emerged from the stifling stratosphere of fame and wealth as the same Nong May - Thai for Little May - she has been affectionately known her whole life.
She is still the devoted daughter of honest, hard workers: Kumpan is into her 23rd year at Banthongyord; her father Winutchai runs a papaya salad shop on the next street.
She is still just another trainee of the school, who dons the same yellow-and-black uniform required of every student - with one distinction: She uses fresh supplies of shuttlecocks from tubes in a box labelled "For Ratchanok Only" while others use bent, battered ones.
She still shares a hostel room with three others in the school compound in the Bang Khae district more than an hour's drive from Bangkok, rather than live it up like a top athlete.
Her family is her mainstay and their rootedness her lodestar. She said: "It's one thing if I'm called a superstar because of what I did on court, but another to actually live like one. My parents are still here, they live simply.
"It's not a luxurious lifestyle, but it's a happy and better one."
Said coach Xie: "This is something that's very precious about Ratchanok. She had nothing in the past, she has everything now, but she hasn't let it get to her head or change her."
The narrative arc of her career, however, is now undeniably and irrevocably different. No one expecting anything from her once is now everyone demanding only success from her.
Her performance on court, and her behaviour off it, has an effect on - take a deep breath - her parents and 11-year-old brother; the badminton school that groomed her; its benevolent owner she sees as benefactor and also calls Mum; the coach who has known her from birth; the corporations that back her with millions; a city and ultimately, a country pining for its first Olympic badminton medal.
It is a burden that would crush even the strongest of weightlifters, yet does not overwhelm this shuttler's slender frame.
She stands tall today because she once crumbled.
Her mind wanders to London's Wembley Arena in 2012, the site of her most devastating loss. That Olympic quarter-final collapse while one game up and five points from victory against China's Wang Xin left her with sleepless nights.
At 17, she wanted to quit. Now, she knows that loss put her on the path to winning.
"It would be too much burden for a normal 21-year-old, but not me," she said. "I'm strong enough to shoulder the expectations. I've experienced so much in my athletic life and they've made me strong both physically and mentally.
"People pin their hopes on me because they believe in me. I also believe in myself."
This belief has sustained Ratchanok in the pursuit of three goals. The first, to become world champion, has long been checked off the to-do list. The world No. 1 ranking is out of the way too. All that remains is standing on an Olympic podium.
She said: "I'm older now, I'm strong, and I've got more experience. It's not just others who have high hopes, I'm expecting something from myself too.
"I'm not afraid to say I want to win a medal because I'm confident that I can really do it."
For someone who never thought she would be a representative - much less a champion - each moment competing with the Thai flag on her chest is a proud one.
"It's like I'm fighting for everyone in my country," she said. "It's why I make the sacrifices, endure the tough training, because not everyone can be given this honourable duty. Thailand may not be famous in many sports but I can show that we can succeed if we work hard enough."
Her badminton journey began with expediency - to get that mobile phone, to buy that washing machine for her mother (as she did after the 2013 World Championships) - but the quest is now fuelled by something greater.
She said: "I was born the daughter of poor factory workers. All the opportunities I've had should not have been available to someone like me."
It is past 9pm as she gingerly walks out of the hall, another gruelling, physical day in the books. The hall will go dark and quiet again.
The next sound it hears will be the footsteps of the champion, walking to work in the early morning.