The Democrat and Bhumjaithai parties have agreed to pair up as "a political duo" to use their combined number of 103 MPs as a way of increasing leverage to bargain for cabinet seats, a source said.
Meanwhile, Future Forward Party (FFP) leader Thanathorn Juangroongruangkit announced that his party will move to persuade political parties which have yet to join a Pheu Thai-led coalition to form a coalition government with his party as the core.
This is seen by observers as a bid to persuade the Democrat and Bhumjaithai parties to join an alliance led by his party.
The Democrat and Bhumjaithai parties have not yet committed their support to the Palang Pracharath Party (PPRP), which has proposed Gen Prayut Chan-o-cha as the prime minister again, to form a coalition government.
A source at the Democrat Party told the Bangkok Post that key figures of the two parties have agreed to become "a duo of political allies'', adding the Democrat Party, which has 52 MPs, will partner with Bhumjaithai's 51 MPs, to negotiate with any parties when it comes to forming a coalition government.
"We will work together as a pair with 103 MPs so as to increase our bargaining power,'' said the source who is a close associate of the Democrat Party's new executive board. Key ministries which are targeted by the parties include finance, transport and energy, the source said.
The source said some key members of the PPRP had tried to contact key figures of the Democrat Party, though the parties had not yet begun any talks because the Democrat Party has to wait for a meeting of new executives and MPs to decide on the party's stance, after Jurin Laksanavisit was elected on Wednesday as the party's new leader.
The procedures should be finished by Wednesday when parliament convenes its first meeting, Mr Jurin said.
"There is still time. Things can start when party executives and MPs meet to decide on the directions the party will take in terms of working in parliament and managing its political future,'' he said.
However, a political alliance led by the Pheu Thai Party, including the FFP, has been relentless in its efforts to persuade the Democrat and Bhumjaithai parties to join it and prevent the PPRP's bid to form a coalition government.
Mr Thanathorn said on Thursday his FFP will be the core of the next government with him as PM if he succeeds.
"We believe only Future Forward could heal wounds and conflicts and bring parties together to share a common stance and ideology," Mr Thanathorn said on his party's Facebook.
"This means sending soldiers back to their barracks and amending the constitution to pave the way for a democratic election. Only we can fulfil this mission."
While the statement does not name any other party, it is common knowledge there is no love lost between the Democrat and Pheu Thai parties, given the deep-rooted animosity supporters of the two parties felt toward each other over the past 20 years of polarising conflicts.
Meanwhile, Bhumjaithai leader Anutin Charnvirakul said he has yet to discuss with any camp ideas for the next government's formation. Bhumjaithai's stance is expected to become clear on May 20 when the party's executives and MPs meet, he said.
He said his party has four principles for considering joining any coalition.
They are the coalition must respect the monarchy, it will not create conflicts, the coalition must have stability, and people's economic problems must be solved.
The pro-regime front has gathered 137 MPs to date, compared to 245 under Mr Thanathorn's coalition. The Democrats, with 52 MPs, Bhumjaithai (51), Chartthaipattana (10) and Chartpattana (3), totalling 116, remain undecided.
To get a prime minister, a majority vote of both houses is needed, or 376 of 700. Assuming all 250 senators vote for Gen Prayut, he will sail though with 387 votes. But Gen Prayut will find it hard to pass key bills if his alliance controls only 137 MPs in the House.