YANGON (Reuters) - Like many of his generation, the head of Myanmar's powerful military is a recent but enthusiastic convert to Facebook.

On his profile background picture, the commander-in-chief gives a "thumbs up" from the cockpit of an airplane. Posts show him celebrating new year in a traditional boar tusk headdress and visiting wounded soldiers.

It's a far cry from just a few years ago, when the only glimpse into the work of the military top command came in turgid reports from state media, and offers a daily reminder that the changes sweeping the South-east Asian nation have reached even the secretive generals who ruled for almost 50 years until 2011.

As he cements his position as de facto No. 2 on Myanmar's post-election political scene, Senior General Min Aung Hlaing has transformed himself from taciturn soldier into a politician, public figure and statesman, say diplomats in Yangon.

"It was like speaking to a politician," said one senior Western diplomat of a recent meeting. "Not a soldier."

People who know him say he is keen to show the army - still loathed by many after decades of iron-fisted junta-rule - is a positive force in the transition to democracy, but also that he is in no hurry for the military to step back from politics.

Until Aung San Suu Kyi's National League for Democracy (NLD) won a resounding victory in the first nationwide democratic election for 25 years in November, Gen Min Aung Hlaing had never had a one-on-one meeting with the Nobel peace laureate.

Since then, they have met at least three times as the historic foes of the army and NLD try to reach agreement on how they will work together once a drawn-out power transition is completed at the end of March.

Gen Min Aung Hlaing has shown no sign he is prepared to give up the 25 per cent of seats in Parliament reserved for unelected soldiers, nor of allowing a change to the junta-drafted Constitution that bars Ms Suu Kyi from becoming president.

"The time is not ripe yet. It is still early," he said when pressed on when the military would return to barracks, according to the transcript of an interview with the Washington Post uploaded to his Facebook page shortly after the election. "The best time may come when there is total peace and stability in the country."

Under the Constitution the commander-in-chief, not the civilian president, appoints the heads of the home, defence and border security ministries, giving the military control of Myanmar's civil service and security apparatus.

With media reports that Gen Min Aung Hlaing's term will be extended by five years, he will be the second most powerful figure in government, after Ms Suu Kyi, for the duration of the NLD's term.

The military's reluctance to step back from politics completely, despite the overwhelming popular vote for the NLD, has been criticised by Western nations and human rights groups, who also accuse it of continuing abuses.

Myanmar's generals say they have a duty to hold together a country fractured by ethnic conflicts until they deem its democracy is stable and durable.

Gen Min Aung Hlaing has studied other political transitions, and makes much of the need to avoid the chaos seen in Libya and other Middle Eastern countries after regime change in 2011.

Brazil's Ambassador to Myanmar, Alcides Prates, said the commander-in-chief told him at a meeting in the capital, Naypyitaw, in January: "We are not going to let Myanmar become an Arab Spring failure."

Gen Min Aung Hlaing did not respond to an interview request from Reuters.

Gen Min Aung Hlaing steered clear of the political activism that was then widespread while studying law at Rangoon University from 1972 to 1974, according to a retired senior law officer who was a contemporary. "He was a man of few words and normally kept a low profile," the classmate said.

While fellow students joined demonstrations, he made annual applications to join the country's premier military university, the Defence Services Academy (DSA), succeeding at his third attempt in 1974.

According to a member of his DSA class, who spoke on condition of anonymity, he was an average cadet.

"(He was) not an outstanding student. Not a driven person, (but) not a lazy person," said the classmate, who still sees Min Aung Hlaing at the intake's annual reunion dinner.

"He was promoted regularly and slowly," added the classmate, who said he had been surprised he had risen beyond the officer corps' middle ranks.

A key goal of Gen Min Aung Hlaing has been improving the image of the military, said Mr Maung Aung Myoe, author of Building the Tatmadaw: Myanmar Armed Forces Since 1948, who says he wants the military to be seen as "the sons and daughters of the people".

The Senior General's Facebook page, launched in 2013, has become his main tool for interacting with the media and public, amassing more than 450,000 "likes", with near daily posts detailing his activities and meetings with visiting dignitaries.

"He understands the military, for the last few years, has had a negative view and a bad reputation," said Mr Maung Aung Myoe. And he has tried to improve it a lot."