The fireball spectacle, or what the locals call Bung Fai Pha Ya Nak, reportedly occurred more than 200 years ago. It happens on the full moon night of October, along a 300km stretch in Nong Khai, the north-east province of Thailand, bordering Laos.

It was the highlight of a five-day educational media trip to north-east Thailand and Laos that I was a part of, along with others from the Singapore print and broadcast industry.

The fireballs have become the main draw for the two-day celebrations that include light shows, boat contests, food offerings and traditional Thai shows.

However, there is no guarantee that they will appear every year.

The mood was electric as the crowd of about 10,000 started filling in as early as 6pm. They would stay till midnight, sustained by barbecued giant freshwater-fish, tom yam soup and Thai beer.

You will know it when the fireballs are out. The people will cheer, says Mr Nittaya Aumbhitaya, director of Tourism of Thailand of the nearby Khon Kaen province.

'You look up and they're in the air,' he says.

Asked if he has seen the fireballs himself, he says that he has every year.

'Last year, I saw three from here,' pointing at the river next to our dining table.

What causes the fireballs remains a mystery. But theories abound.

SUPERNATURAL?

The Nong Khai Thais, being devout Buddhists, believe the fireballs come from Naga, or serpent, as a form of spiritual homage to the Buddha.

Our tourist guide, Ms Veena Puntace, says of the fireballs: 'Initially, I believed the scientific explanation of the fireballs. But then I meditate too, and also, how do you explain the timing?'

The end of Buddhist lent coincides with the eleventh full moon, which is when the fireballs occur.

SCIENTIFIC?

Scientists however, have another explanation. They hold that the fireballs are the result of a series of natural forces at play.

In October, there is an abundance of plant and animal life decomposing at the bottom of the Mekong. These emit flammable natural gases as the sun beats down on the river. At night, these gases are released by the gravitational pull of the moon, at its strongest when it's full.

In a New York Times article, the Tourism of Thailand authorities apparently claimed that they had the chemical composition of the fireball sorted out: methane-nitrogen gas with aerobic and anaerobic bacteria that sparks when it rises and mixes with oxygen.

OR MAN-MADE?

A Thai TV station said that the fireballs were actually rounds of tracer ammunitions. The tracer rounds were supposedly fired on the other side of the riverbank by Laos soldiers who were using AK47 rifles.

This version did not go down well with Buddhists. Hundreds were reported to have gathered to protest against the TV station's version of the event last year. Mr Surasee Pathum, a Nong Khai film director who has completed a documentary on the fireballs, said: 'How many bullets will the Laos soldiers fire? A lot. Now, why would the Laos soldiers do that, to fool the world?

'Besides, the colour and the speed of the Naga fireballs are very different from that of bullets.,' he said

ALIENS

Watching the documentary VCD I bought at the site, I can't help but think of UFOs. But let's not go there.

It would have been easier for me to write what I think about the fireballs had I witnessed it myself. Sadly, in the four hours I waited, the only things that shot up from the riverbank were the numerous fireworks set off by excited members of the crowd.

By 10pm, the crowd had mostly thinned, with the intention of coming back the next night, which, after all, was Laos' full moon. The joke that night was that Naga was a Laotian. So it would definitely fire those balls the second night.

Whatever the Naga fireball was, the general consensus among the Singapore media group was of acceptance.

The phenomena has moved a large number of people into believing in something that gives them hope, faith and I believe, happiness. The Naga fireballs have become inspirational, something to look forward to each year.

Much like Singaporeans' joy in anticipation of their National Day Parade. Only this one is on a more spiritual level.

We would have gladly stayed for the second night but we had to go. Who knows, maybe next year?

YOU can reach Khon Kaen and Udon Thani from Bangkok by flight and road (local coach).

From Udon Thani or Khon Kaen, take a coach to Nong Khai. The domestic airfare from Bangkok to Khon Kaen by Thai Airways is 1,500 baht (one way, including taxes) and by Air Asia it is 599 Baht (one way, excluding taxes).

Details are available at www.thaiairways.com and www.airasia.com. Flying time is 1 hr and 5 mins.

The air-conditioned coach fare from Bangkok to Khon Kaen and Udon Thani is about 500 Baht. Go to www.transport.co.th for details.