Yesterday was the last day for constituency candidates to register. The three main opposition parties - Democrat, Chat Thai and Mahachon - are boycotting the April 2 snap election.

As a result, Thai Rak Thai stands to capitalise in regions where its popularity lags behind that of its rivals.

The South is the Democrat Party's stronghold, Sa Kaew is the base of rebel Thai Rak Thai faction Wang Nam Yen, Suphan Buri is Chat Thai Party's home , and Phichit is Mahachon Party's base.

"The fear we wouldn't garner the required 20 per cent of eligible votes [in certain constituencies] is no longer a problem because there is more than one candidate in those areas," said a Tha Rak Thai executive member who asked not to be named.

In a constituency where only one candidate is running, the candidate must win at least 20 per cent of the eligible votes to secure a parliamentary seat, according to Article 74 of the election law. If the candidate falls short of the margin, a new poll must be held. A new government cannot be formed until all 500 candidates of the House have been elected.

In numerous constituencies in the North and Northeast, the Thai Rak Thai is the only party fielding a candidate. With both regions being party strongholds, it will have little difficulty in securing the minimum 20 per cent of the vote.

Of 400 constituencies, 123 Thai Rak Thai candidates are lone candidates, mostly in the North and Northeast. In Chiang Rai, Phayao, Samut Sakhon and Amnat Charoen, Thai Rak Thai candidates stand alone.

In Bangkok's 36 constituencies, candidates from 15 parties have registered. Three parties - Thai Rak Thai, the Thai Citizen Party, and little-known Thai Ground Party - will be fielding candidates in every constituency.

In the South, Thai Rak Thai will face competitors from little-known parties, such as the Thai Chuay Thai Party and the Progressive Democratic Party.