Factbox: Pre-election opinion polls in Thailand

(Reuters) - A July 3 parliamentary election in Thailand is expected to be a close race between the ruling Democrat Party and the opposition, Puea Thai, whose previous incarnations have finished first in every poll in the past decade.

Early opinion polls have put Puea Thai slightly ahead of the Democrats, but a sizable percentage of respondents are undecided.

Although Thai surveys are regarded as indicative of the pubic sentiment, they have fairly large margins for error, often as high as seven percent.

DUSIT POLL (Suan Dusit Rajabhat University, Bangkok)

A May 22 poll of 3,584 respondents showed 41.2 percent backed Puea Thai, with 36.9 percent for the Democrat Party. The medium-sized Bhumjai Thai and Chart Thai Pattana scored just 3.9 and 3.2 percent respectively, with six percent undecided.

BANGKOK POLL

Its survey released on May 23 put Puea Thai as the favorites to win in Bangkok, with 25.8 percent, ahead of the Democrats at 14.7 percent in their stronghold. However, 52 percent of the 1,178 respondents were undecided.

ABAC POLL (Assumption University, Bangkok)

ABAC's May 22 survey centered on a variety of leadership qualities of Prime Minister Abhisit Vejjajiva of the Democrats and Puea Thai's prime ministerial candidate, Yingluck Shinawatra. The poll of 2,300 respondents showed views of Abhisit's leadership was on the decline compared to previous months, with Yingluck's overall rating climbing.

(Compiled by Martin Petty; Editing by Jason Szep)