Sunday morning in a back street of Otahuhu, and a large, red brick bungalow is decked out with stalls in the garden. Monks in saffron robes sit on mats. Small women wearing beautiful silk skirts arrive with food.

This is a Laotian Buddhist temple, but its members have turned up to hear from a couple of blokes who seem from another existential plane entirely: two Auckland ad men with the motorbikes and chin stubble that would usually speak of mid-life crisis.

The two brothers seem large, but not out of place. Geoff Collins starts an audiovisual presentation about the work he and his brother Martin are doing with the Bridging the Gap Mekong Trust, building schools in the remote north of Laos where there are no roads, no phones, no distributed electricity.

The Laotians here have never heard of these villages. A few know the name of the closest town Oudom Xai, but no one has been there. Nevertheless, the local community is interested in helping.

The two men are close, obviously brothers with similar voices. They are fit-looking, greying, their feet light and their eyes lively. They talk fast - as any self-respecting ad man should, perhaps. Their stories range all over the place as one takes up the tale from the other.

For the past six years, the two have been journeying up the Mekong River to help isolated and under-privileged children living hand-to-mouth existences in villages crushed between the tropical jungle and the river, their only contact with the outside world.

Incredibly, these two blokes with their motorbikes had decided to build schools for the kids of the Mekong Highlands.

There is enormous civility and welcome from the people of the temple, down here in Otahuhu. Regardless of the motorbikes and stubble, the brothers seem to have earned their respect.

It all started when Geoff and Marty set out on another of their adventures exploring Southeast Asia by trail bike, they explain later. Marty turns up for an interview on a grunty new black 900cc Triumph Bonneville.

Geoff, 60 and married with one child, has worked across Asia Pacific for the past 12 years in senior advertising management. Marty, 55, divorced with one child, has worked in advertising for more than 26 years, and produces TV commercials.

Since 1998, the two busy brothers - bike riders since their teens - have hooked up on their holidays to ride motorbikes in Asia, a rather exciting choice of holiday, to say the least.

Everything is a challenge, they say. A route that on the map looks like a two or three hour ride will end up taking 12 hours, fording rivers. You stop for a drink in the middle of the jungle, turn around and there is one guy carrying an AK47, another with what looks like a blunderbuss. They're hunting birds, curious not hostile.

It's another world from Geoff's ex-pat condo in downtown Bangkok, or Marty's all-mod-cons St Johns townhouse.

In 2003 the brothers set out again, crossing the border from Thailand into Myanmar, where you could buy tiger and snow leopard skins at the market at Tachilek, and then further east, back into Laos and north to near the Chinese border at Muang Sing.

Laos is a mountainous, landlocked country, and a lot of it you have to travel by river. Accordingly the brothers had to load their Honda 250 trail bikes on to long boats when they reached Xieng Kok, close to the opium growing region of the Golden Triangle.

They recall the boats pulling in for a night at the remote village of Ban Hatteu.

They left their packs on the boat, as asked, and waited in a house not knowing where they were or what was going on. No one spoke English, and people were "gawking". .

"Kids would run up take a look, and run away again. We were probably the first white people who had ever been there," says Marty.

The brothers, concerned about their gear on the boat, were taken to another house where they assumed they were expected to rest.

Says Geoff: "We were lying in the dark wondering what was happening, when all these people came upstairs with lanterns, taking us by the hand and leading us downstairs for dinner. It was fantastic. We had this wonderful night."

The next day, says Marty, they were returned to the boat where they saw their packs had been examined.

"There wasn't one tiny thing, not a pocket knife, not a roll of film, not a roll of banknotes, nothing had been taken."

These were days when foreigners came across as walking millionaires, days when the country had no ATMs or credit card facilities. The brothers carried a lot of cash, and their motorbikes were worth more than the villagers would earn in a lifetime.

"If you ever went missing, no one would even know where to start looking," says Geoff. "Nobody."

Instead of feeling threatened or robbed, the brothers recall only unforgettable hospitality and friendship from the locals this from people whose children, unlike their own, had no toys, no books, nothing much at all.

"It's not much of a childhood," says Marty.

This prompted the Collinses to help by firing off a request to associates and friends for children's picture books. They were swamped. NZ Post helped with freight; the Lao consulate in Canberra waived duty. Soon they were raising funds for school desks, chairs, roofing iron and blackboards.

So, in 2006, they turned their attention to a new school here, which villagers using hand gestures had asked them to help rebuild on cleared land.

The brothers weighed up the possibility, realising a bit more money on top of leftover cash from fundraising would secure the $16,000 needed to give the children a schoolhouse to be proud of.

Soon the Ban Hatteu schoolhouse was reborn with translating help from Geoff's Thai secretary, and some rough and ready building techniques from the locals who hauled cement mix up from the river.

"Tiny women," says Marty, "have a fabric band around their heads going on to their back, and each woman would carry a sack ... bare feet so they could get a grip on the earth, going up this bank that's at 50 degrees and chatting to each other as they're doing it. I wouldn't walk three metres with one of those things."

In 2007, investment adviser Gareth Morgan (a fellow motorbike adventurer) helped the brothers with a second school at Ban Lad Khammune, replacing a rundown facility too small for the 120-plus children being taught in two classes in one room. Youngsters had to be moved around the dirt floor to stay dry during the rainy season.

This year the men are close to completing a third school at Ban Lad Hane (Lester Wunderman Secondary School) after securing finance from global advertising company Wunderman, and having delivering its chairman and chief executive Daniel Morel upstream to experience the project first-hand.

Again, the existing village school was in desperate need of replacement about 360 students studied in six classrooms with dirt floors, large black scorpions, bamboo walls and leaky roof. As one of only two secondary schools on a 150km stretch of river, many students boarded in crowded dormitories.

Building the school was, again, a village responsibility. Each family was expected to make a certain number of concrete blocks, between fishing and farming.

"If they don't get involved there's no ownership, so you need that," says Geoff.

Already the brothers have requests for more schools, but the trust will build and fit out future schools only where there is already a teacher.

Geoff visits two or three times a year from Bangkok; Marty perhaps once a year. Trustees pay for the trips themselves - that's one of the founding principles. Trustees volunteer their time, and no management or administration fees are deducted from donations.

"It's amazing what a bit of goodwill and generosity and getting stuck in can do," says Peter Biggs, the trust chair and Clemenger BBDO's Melbourne managing director.

"Contrary to what people might imagine, people in advertising are not all rapacious ... self-interested, self-absorbed hedonists, they're actually really smart and very generous."

Aucklander Angela Griffen has travelled up the Mekong River and seen the challenge for herself. She says the brothers are not guys who need something to do with their lives; they are not "do-gooders", they just "do good".

"They absolutely live life to the fullest, and they believe that a bit given from your life reaps a great return."

Griffen says the projects are on a par with those she has been associated with through the Fred Hollows Foundation (providing eye operations and lenses in Nepal) and with Ray Avery and Medicine Mondiale (giving medical and scientific solutions to the developing world).

"A lot is done long-distance and having faith in others. Somehow that trust and belief makes it happen."

Geoff and Marty, who grew up in Auckland's Mission Bay and attended St Kentigern School and King's College, say it is unlikely they would ever have been drawn to philanthropic work in New Zealand.

"What I encountered in Laos were people with absolutely nothing who opened their hearts and their homes to us and made us feel unbelievably welcome," says Marty.

He is impressed by the strength of Laos' family values, living in 700-year-old villages that its people never leave.

"The children take care of the babies while mum and dad work, and that family takes care of the grandparents and that's how life goes, it's a cyclic thing."

But the arrival of satellite dishes and televisions (run on car batteries and generators) are opening villagers to other influences.

"Suddenly you've got young Lao women going to work in the bars in Thailand and you've got young Lao men going off to work on construction sites for US$3.50 ($5) a day in horrendous conditions, and although money is sent back to their families, it's leading to a breakdown in traditional village life." Education, say the brothers, is a solution.

"Maybe they can retain their identity within Laos and maybe earn within Laos rather than having to go to other countries, and so keep the family closer," they say.

"That's important to us."

To find out more visit: www.bridgingthegapmekongtrust.org