The preliminary round of talks follows last December's Cancun, Mexico, summit during in which countries pledged $100 billion a year in aid to poorer nations by 2020 and agreed to a maximum 2 degree Celsius global temperature rise.
The European Commission's top climate negotiator, Artur Runge-Metzger, said the crisis at Japan's crippled Fukushima nuclear power plant would have an impact on the climate talks.
"There will be a lot of political considerations and they have repercussions here in Bangkok and during the year because we haven't seen the end of what is going to happen in Fukushima," he said Sunday, Kyodo news reports.
Japan may review its target of reducing greenhouse gas emissions by 25 percent in light of the ongoing nuclear crisis, top government spokesman Yukio Edano hinted Monday.
Thailand's deputy chief climate negotiator, Sangchan Limjirakan, said the devastating floods and landslides that have battered the region since March 23 was caused by global climate change.
"This climate-related disaster has never been witnessed in Thailand before," she said, Xinhua news agency reports.
Speaking at the opening of the conference, attended by some 1,500 ministers and diplomats, U.N. Framework Convention on Climate Change Executive Secretary Christiana Figueres called for governments to resolve fundamental issues over the future of the Kyoto Protocol.
Kyoto is the world's sole existing agreement in which nearly all industrialized countries agreed to internationally binding commitments to reduce emissions over time.
The first phase of Kyoto expires at the end of 2012. Some developing countries, including China, India and Brazil, favor renewing Kyoto, while some developed nations prefer replacing it.
"Governments need to figure out how to address this issue and how to take it forward in a collective and inclusive way," Figueres said. "Resolving the issue will create a firmer foundation for a greater collective ambition to cut emissions."
So far, she said, the sum of national promises equals only about 60 percent of what is scientifically required by 2020 to stay below the agreed-upon 2 degrees Celsius goal.
Figueres also called on governments to deliver the funding and technology aimed at helping developing countries deal with climate change.
The Bangkok meeting, which concludes Friday, is hoped to pave the way for progress at December's summit in Durban, South Africa.