Thaksin was addressing hundreds of delegates, including UN Secretary General Kofi Annan and actor Richard Gere, when the group unwound the four metre wide banner before being ushered out of the conference hall by security guards, on Sunday.
A group of a dozen people continued to stand quietly at the back of the hall holding banners saying: "No more lies" and "Clean needles now".
The government's budget for prevention programmes has been slashed by nearly two-thirds since 1997, to just $2m a year, according to the UN, after Thailand's programme to tackle HIV in the 1990s was hailed as a model for the world.
A UN report last week said there were clear warning signs of a new wave of infections in Thailand.
Earlier, about 1000 people, most of them HIV-positive, protested at the 15th International AIDS Conference over the shortfall of cash to fight the global pandemic.
Hundreds of Thais carried placards calling for better treatment in a demonstration outside the convention hall where some 17,000 experts, scientists, activists and leaders will gather over the next six days.
"Where's the 10 billion? Treat the six million!", read one large banner, referring to the $10bn donor governments pledged in 2001 towards the AIDS fight by the year 2005, and the six million HIV-infected persons worldwide who need immediate treatment.
"Where's the 10 billion? Treat the six million!"
"Break the patents, treat the people!"
Protest banners at the Aids conference
"George Bush, shame on you," marchers chanted, referring to the US president who they say has withheld money from a global fund so his administration can pursue its own bilateral programme.
"Break the patents, treat the people!" said another banner, addressing one of the most contentious issues at the summit, the battle of cheap generic drugs versus patented brand-name pills produced by the world's pharmaceutical giants.
"We're protesting because it's been two years since the international community promised to drastically scale up treatment, but since then they have defunded the Global Fund, and George Bush has refused to fund science-based programmes that are proven to work," reporters were told.
"Asian nations face a choice. They can act now or pay later," Peter Piot, executive director of the UN agency UNAIDS, said bluntly as the six-day forum got under way.
"This conference must be a wake up call for Asian leaders. They are starting to respond but, I think, too timidly," Piot told reporters.
Around 20 million people have died of AIDS since the condition was identified in 1981, and around 38 million people have the human immunodeficiency virus that causes it.
Two-thirds of them live in Africa, but Asia is fast catching them up.
Of the 4.8 million new HIV infections last year, a quarter were in Asia. Around 7.4 million Asians now have the virus, and the big population centres of China, India and Indonesia are especially at risk, UNAIDS says.
"Asian governments unfortunately are still burying their heads in the sand ... the way the South African government did a few years ago," South African AIDS activist Zackie Achmat warned.
"Asian nations face a choice. They can act
now or pay later. This conference must be a wake up call for Asian leaders. They are starting to respond but,
I think, too timidly"
Executive director of the UNAIDS
Tim Brown, an epidemiologist with the East-West Centre, said Asia had "an incredible diversity" of HIV epidemics linked by a common threat.
In every country, pools of infection are initially limited to gays and injecting drug users.
Two or three years later, though, infections among the drug users would spread to sex workers, of whom they were often clients.
From the sex workers it would then spread out into the wider community. Men who visited prostitutes would come home and infect their wives, who would then infect their babies if they were pregnant.
The pace at which this happens depends very much on the sexual habits of the country, Brown said.
In Thailand and Cambodia, HIV spread like wildfire in the 1980s because so many men, 20% of the adult male population, visited prostitutes.
So many people fell sick and died that the countries acted commendably quickly to distribute condoms and encourage safe sex, Brown said.
Since 1990, condom use among Thai sex workers has risen to almost 90% and the number of clients has halved. "Over six million infections were averted," he said.
But in other countries, where sex with prostitutes is less common, HIV cases have risen slowly, with the risk of complacency, Brown said.
"In the countries where 10% of men visit sex workers, such as China, we expect to see the epidemics starting their faster growth only now," Brown said.
The International AIDS Conference in Bangkok is the first time that this major event, held only once every two years, has been held in an Asian developing country.
China has sent more than 500 delegates to the forum, its highest attendance ever, and 10 times more than the American delegation.
Shortage of doctors
Meanwhile, a report issued at the conference warned that shortages of doctors to supervise the distribution of anti-HIV drugs in Asia may unleash "treatment anarchy" that would help breed resistant strains of the virus.
Ministers from countries in the
region also attended
China, which has some 840,000 infected individuals, has fewer than 200 doctors who have specific training in treating HIV and AIDS, the report by TREAT Asia, a programme of the American Foundation for AIDS Research, said.
The report also states: "In India, which is expected to surpass South Africa in 2006 as the country with the single highest number of HIV infections in the world, there are only an estimated 500 trained doctors, or roughly one trained doctor for every 10,000 HIV-positive individuals."
The situation is even worse in Vietnam, where there is just one trained doctor per 11,250 people.
Disaster looms if patients try to treat themselves by buying the drugs over the counter at pharmacies, a frequent practice in Asia, the report said.
"The consequences of widespread 'self-medication' can be catastrophic. As patients under-medicate or treat HIV with incorrect dosages, the potential for the emergence of drug resistance is significant."