It has been promoted as a showcase for the new Myanmar, a regional sporting event in December that will celebrate the country’s embrace of democracy and the end of a hermetic and oppressive era.

But the Southeast Asian Games, which will be held in Myanmar’s capital, Naypyidaw, and other sites throughout the country, is causing acrimony long before a single athlete has competed.

Malaysia, the Philippines, Singapore and Thailand, which all intend to participate in what are known as the SEA Games, have sent separate letters to Myanmar protesting the way the event is being organized, according to Gen. Yuthasak Sasiprapha, the president of the National Olympic Committee of Thailand.

"These games are supposed to bring unity, but they are causing divisions instead," Yuthasak told the Thai news media last week.

The main complaint is that Myanmar, formerly Burma, has stacked the competition with obscure sports that Myanmar’s athletes have a good chance of winning.

Charoen Wattanasin, the vice president of the Thai National Olympic Committee, said in an interview that the SEA Games regulations allowed for eight traditional sports but that Myanmar had put 14 on the roster.

"Nine out of the 14 are martial arts," he said, struggling to describe them. "They are — well, I can’t even remember their names."

One is called chinlone, a traditional Burmese game that mixes dancelike acrobatic movements with what might be described as soccer juggling skills. There is no opposing team, and competitors are scored in a manner similar to those in gymnastics.

Myanmar has dropped tennis and table tennis from the games, even though both have been played in all SEA Games since the competition began in 1959. Gymnastics is out, as is badminton, Thai and Philippine officials said.

The Singaporeans are lamenting the loss of water polo, in which they do well, and the Philippine Olympic Committee has threatened to send a threadbare delegation if the roster is not changed. Malaysia and Indonesia, which have strong badminton traditions, are urging that the sport be reinstated.

The Nation, a Thai daily newspaper, reported Sunday that Myanmar had also dropped beach volleyball because "the sport’s outfits were not suitable for Myanmar culture."

Myanmar circulated the roster of events to representatives of participating countries last week and for now is defending its selection.

"Every host country has the authority to decide which competitions should be included and excluded," U Htay Aung, a director in Myanmar’s ministry of sports, said in an interview Sunday.

Htay Aung said he recalled previous games in which Myanmar’s requests "were ignored."

"There are always complaints at these games," he said. "Myanmar will make the final decision."

Myanmar will hear from the 11 countries competing in the games at meetings in Naypyidaw on Monday and Tuesday to discuss preparations.

"If they continue to push through this proposal, it’s worthless to hold the games," Charoen, the Thai official, said.

Myanmar’s ability to organize the games smoothly will be closely watched by officials in the region, because in some ways it will be a test run for a much more ambitious project. Next year, Myanmar will hold the chairmanship of the Association of Southeast Asian Nations, a responsibility that involves playing host to countless regional meetings and dealing with thousands of visiting diplomats and journalists.

It is a challenging task for a government that is only now breaking from its inward-looking, military past and its history of antagonistic relations with the outside world.

Myanmar appears eager to reassure its neighbors that it is ready to host the games. U Naw Tawng, a Burmese official quoted on Myanmar’s official SEA Games website, predicted that the games would be better than those held in 2011 in Indonesia.

Myanmar has played host to the games twice — in 1961 and 1969 — but this is the first time the games are to be held there since the brutal suppression of the democracy movement, including a bloody crackdown in 1988.

The country is in the middle of a wrenching transition from military rule to democracy led by President Thein Sein, who heads the country’s first civilian government in five decades.