Thailand's main opposition parties have rejected the prime minister's offer to include them in a new government if he is re-elected in next weekend's poll.
Mr Thaksin is facing the biggest challenge of his career
Thaksin Shinawatra made the offer after weeks of protests by demonstrators calling for his resignation.
The opposition parties are boycotting the elections, which Mr Thaksin called in an effort to regain legitimacy.
Tensions remain high, and a small bomb was found at the office of the opposition Democrat Party on Monday.
It was successfully defused by police before it was rigged to go off, said party spokesman Hong-art Klampaiboon.
There has been no information on who might have planted the bomb, but it is the latest of several small explosive devices to be found in recent weeks, thought to be linked to the current political crisis.
Mr Thaksin said late on Sunday that if he was re-elected, he would offer his opponents important positions in his new government, even if they had not taken part in the election.
He told Thai media that forming such a government would be "the way to bring unity back to the country".
Senior members of the opposition and leaders of the anti-government protests were both included in the offer.
The anti-Thaksin marches have become a weekly fixture
But all sides appear to have rejected Mr Thaksin's olive branch.
Late on Sunday night, Sondhi Limthongkul, one of the main leaders of the anti-Thaksin demonstrations, said the prime minister was "insane".
"He proposed a government of national unity and invited us to join after he labelled everyone against him as the bad guys," Mr Sondhi told Thai television.
On Monday the opposition parties also refused Mr Thaksin's offer.
"I think this is Thaksin's new joke," said Hong-art Klampaiboon, spokesman for the Democrat Party.
"His point is only to have the election and not to worry whether it is a dirty election or not," he said.
Meanwhile the anti-Thaksin demonstrations are continuing. The latest rally on Sunday saw tens of thousands of protesters marching through Bangkok's central shopping district.
More protests are planned later in the week in the run-up to Sunday's poll.