Polls took place last week in the Himalayan nation for the largely ceremonial 25-seat National Council that are seen as a warm-up for the main electoral contest for the National Assembly from which the next government will be chosen.
Five parties are contesting the first round of the balloting on May 31 and the two parties which come out on top will compete in a run-off on July 31, officials said in national capital Thimpu.
Bhutan held its first parliamentary elections in 2008 after its beloved royal family opted to step back and peacefully transform the country into a constitutional monarchy.
In 2008, the DPT won 45 of the 47 National Assembly seats while the opposition party wrested the remaining two.
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A political observer, who did not wish to be named, said the DPT had an edge over other parties since it received the approval of 67 per cent of the voters in the previous parliamentary balloting.
Bhutan is famed for its upscale tourism and unique yardstick of Gross National Happiness, which measures the mental well-being of citizens, not just their material wealth.
The nation, sandwiched between India, China and Nepal, has seen widescale development under the centre-right Druk Phuensum Tshogpa party of Prime Minister Jigmi Y Thinley.
But a large income gap, youth unemployment and delinquency, and urban migration have caused discontent among voters.
Despite high interest in the election process, confusion persists about parliament's role in the deeply traditional nation where for decades the monarch's word was law.