Thailand is one of the biggest foreign investors in Myanmar as well as being a key trading partner and has resisted efforts by the US and European Union to impose sanctions in order to push for democratic reforms.
Speaking to reporters on Tuesday Noppadol Pattama, the Thai foreign minister, said his government preferred to follow a "constructive engagement" policy towards its neighbour.
Myanmar's May 10 referendum will vote on a draft constitution which the country's military leadership says will pave the way to elections in 2010.
However the process has been labelled a sham by opposition groups who say the process is intended only to tighten the military's grip on power.
The main opposition National League for Democracy (NLD), led by detained Nobel peace laureate Aung San Suu Kyi, is urging voters to reject the referendum.
Under the proposed charter Aung San Suu Kyi will be barred from standing for office because she was married to a foreigner.
The UN says 74 remain missing after soldiers
the September crackdown [AFP]
Samak Sundaravej, the Thai prime minister, took a less direct line than his foreign minister on Myanmar's referendum, telling reporters: "I don't think I can comment otherwise I will be accused of being Myanmar's mouthpiece".
Instead he compared Myanmar's present political situation to that of Thailand three decades ago "when we had half a democracy".
Samak said he and his Myanmar counterpart are expected to discuss the
referendum, cross-border drug trafficking and illegal immigration.
The problem of illegal immigration into Thailand was highlighted earlier this month when 54 Myanmar migrants suffocated in an unventilated truck while being smuggled into Thailand.
In a separate development on Tuesday the European Union called for an international arms embargo against Myanmar's government and warned of tougher sanctions if the ruling generals fail to improve human rights.
Last Thursday a European Parliament resolution said the existing EU embargo was ineffective because Myanmar's military was still able to purchase supplies from China, Russia and India.
The parliament also called for broader sanctions to prevent Myanmar's generals using European banks or financial services.
EU foreign ministers have expressed concern that Myanmar's constitution would restrict eligibility for high office and said only full participation of all stakeholders, including Aung San Suu Kyi and ethnic groups, would bring reconciliation and stability.
EU governments tightened sanctions on Myanmar after a crackdown on peaceful pro-democracy protests led by Buddhist monks in September.
The protests led to the killing of at least 31 people while 74 are still missing, according to the UN.
Human rights group Amnesty International says more than 700 people are still behind bars over the protests.