A lack of rivals will require Thai Rak Thai candidates to win 20 per cent of the votes in constituencies where they are running solo, a benchmark they are unlikely to meet in the South.

The deputy Chat Thai leader insisted the party would stick to its pre-election agreement with the two other major opposition parties to boycott the election, despite comments from deputy Thai Rak Thai leader Somsak Thepsuthin.

Chat Thai Party leader Banharn Silpa-acha will return to Bangkok from Tokyo today and is expected to consider the matter tomorrow.

The Democrat Party also reiterated its stand yesterday that it would not field any candidates in the second round of voting for 38 constituencies on April 23.

Party spokesman Ong-art Klampaiboon said there had been attempts to spread rumours that either the Democrat or Chat Thai party would field candidates.

He also lashed out at caretaker Agriculture Minister Sudarat Keyuraphan, who earlier had urged other parties to stop making further demands following Thaksin Shinawatra's announcement that he would give up his post as premier.

Sudarat should consider who is amassing unusual amounts of wealth before making such a suggestion or talking about the national interest, Ong-art said.

He also urged the Thai Rak Thai Party to stop claiming that Democrat leader Abhisit Vejjajiva was operating under the shadow of former party leader Chuan Leekpai.

Chuan has never controlled Abhisit, he said.

"The reason Thai Rak Thai makes such an attack is because it's not happy about Democrat criticism over the lack of legitimacy of the Thaksin regime," he said.

"If Thai Rak Thai really examines itself it would realise that over the past four to five years the Thaksin regime had created abuses of power in many respects," Ong-art said.

The real issue now is not who will be become Thaksin's successor but whether Parliament can convene within the time limit stipulated by law, he added.

All 500 seats in the lower house must be filled within 30 days of an election in order for Parliament to convene.

Thai Rak Thai's legal team has said if they fall short after the second vote, they can petition the Constitution Court to make a "flexible" ruling in order to allow Parliament to convene.