Thais and Cambodians alike are puzzled following the abrupt shift of Phnom Penh's policy toward Bangkok. This new policy is more amicable, more compromising and less confrontational.

Cambodian Prime Minister Samdech Hun Sen, in particular, is seen to have enthusiastically welcomed a renewed relationship with his former enemies across the border – Prime Minister Abhisit Vejjajiva and Foreign Minister Kasit Piromya, with potentially ominous personal implications for Thaksin Shinawatra, the deposed Thai Prime Minister who continues to lead protest inside the country from afar.

In Hanoi last week at the sidelines of the 17th Asean Summit, Abhisit met with Hun Sen and engaged in a 15-minute discussion. Abhisit later told the media that Hun Sen had accepted a request from Thailand to investigate reports that some red-shirt leaders with outstanding arrest warrants for terrorism were hiding in Cambodia. Abhisit also said Hun Sen had assured him that Cambodia is ready to throw its support behind Thai authorities if they officially requested it.

On the surface, this friendly development seems to suggest that Thai and Cambodian leaders have forgiven one another for what they did to each other in the past and now want to put differences aside. In his interview with Singapore's press, Kasit declared, "Thai-Cambodian relations are on the mend, especially after the return of our respective ambassadors to their posts. We may have our differences, but I think this is not uncommon for neighbouring countries sharing a common border."

But such flowery diplomatic language fails to shed light on what has really driven Hun Sen to U-turn his country's policy.

In my interview with a self-exiled UDD leader, he admitted that the entire strategy of the current pro-democracy red-shirt movement, which included the UDD, independent groups inside and outside Thailand, former Prime Minister Thaksin Shinawatra and his team, and possibly some members of the Puea Thai Party, has not been uniformly conceived.

This condition could open the door for the radical elements to exploit the movement's ambiguous agenda and strategy. The interviewee also hinted that Hun Sen himself might not be able to confirm that so-called red shirt militants are being trained on his soil. In fact, Cambodian Defence Minister Tea Banh said over the weekend that he did not know if Arisman Pongruangrong, presently charged of terrorism in connection with political violence during the red-shirt protests, is in hiding in his country. And this could explain why Hun Sen was willing to cooperate with the Thai authorities, to find out the truth himself.

It may also explain why Hun Sen has lately been distancing himself from the red-shirt movement and instead befriending the Abhisit government. Back in October 2009, Hun Sen publicly offered his support to Thaksin and the UDD. He stated, "This is just moral support from me. As one million Thai people of the red-shirt group support Thaksin, why cannot I, as a friend from afar, support Thaksin?"

But it becomes clearer now that the red-shirt movement, and to some extent the Puea Thai Party, have been in serious disarray. The fragmentation within the red-shirt camp, partly because most of its core leaders are under detention, has compelled Hun Sen to reconsider whether supporting the red shirts is still in his country's interest.

It is unlikely that the Cambodian government would sacrifice itself or be exposed to such risks without any coherent or winnable strategy on the part of the red-shirt movement. After all, Hun Sen is known to be a calculating political leader and therefore would not play the game if there was no sure bet available.

The red-shirt UDD is not the only casualty in this perplexing diplomatic game between Cambodia and Thailand. Thaksin, too, has become Hun Sen's estranged partner. At the peak of Thai-Cambodian conflict last year, Hun Sen said out loud that Thaksin was his protégé. Hun Sen even made an emotional plea, "Though I am not Thai, I am hurt by what has happened to him. My wife even cried on learning about it and has an idea to build a home for Thaksin to come and stay honourably." As a consequence, Hun Sen appointed Thaksin as a special economic advisor to his cabinet, apparently to irritate the Abhisit government and further complicate Thai politics.

However, the political situation in Thailand has changed drastically within the past six months, precisely after the violent crackdown on street protesters in Bangkok in May 2010. Some red-shirt members were accused of engaging in terrorist acts. Thaksin, increasingly politically marginalized, has been labelled by his opponents as the chief operator of a terrorist network.

Hun Sen may only now realise that Thaksin, once perceived as Cambodia's long-term interest, is slipping away and that it will be very difficult for him to return to power anytime soon. At the same time, he may also observe that Abhisit's Democrat Party, despite currently fighting for its continued existence in the dissolution case, appears to have become much stronger, not so much because it has crafted new political strategies, but because the Puea Thai and the UDD are both becoming weaker and the channels of communication between them have broken down.

As Prime Minister's Office Minister Ong-art Klampaibul said in early September this year, "Hun Sen has voiced confidence that Abhisit will stay in the post for a long time and that the prime minister has grown stronger and proved his leadership skills."

Critics of this government may not want to hear this, but it is highly possible that, under the present political circumstance, the Democrat Party stands a good chance of winning the next election, with the help of certain personalities, like Newin Chidchob. Thus, in the short term and perhaps for the next 4-5 years, the Democrat Party would still be around. The traditional elite are determined to keep the Democrat Party so that it could watch over any major political event or transition within the political domain or key institutions.

Hun Sen might not have the patience or does not want to wait until the day Thaksin comes home. In actual fact, this might not happen at all. Hence, the disintegration of Thailand's opposition and the slim chance of Thaksin's political survival could form the basis of Hun Sen's changing attitude toward Thailand.

Pavin Chachavalpongpun is a former Thai diplomat and now a Fellow at Singapore's Institute of Southeast Asian Studies.