A party that was part of Thailand’s last military-backed government has ruled out joining any coalition that includes the pro-democracy Move Forward Party.

Bhumjaithai Party leader Anutin Charnvirakul said he conveyed the message on Saturday to Pheu Thai Party, which has stepped up to lead the formation of a government with Move Forward and other coalition partners.

Move Forward had won the most seats in a May national election but its leader has been blocked from taking office by conservatives in parliament. Bhumjaithai has the third most seats in Thailand’s parliament.

The coalition now led by Pheu Thai commands a majority in the newly-elected lower house, but the next prime minister needs to have more than half the votes in the combined National Assembly, whose strength is currently at 748. The key challenge is winning the support of the 249-member Senate, which is stacked with allies of the pro-military royalist establishment.

Pheu Thai, the second-biggest winner in Thailand’s May general election, said it will seek the support of the military-appointed Senate before the next prime minister vote, scheduled on July 27.

Bhumjaithai’s message will be conveyed to other pro-democracy alliance parties, Pheu Thai party leader Cholnan Srikaew said after meeting with Anutin. Pheu Thai is backed by ousted former premier Thaksin Shinawatra.

Conservatives in Thailand’s parliament say they are opposed to Move Forward’s campaign promise of amending a so-called lese majeste law that punishes anyone for defaming or insulting the king or other royals. A prominent senator, Kittisak Rattanawaraha, this week said Pheu Thai must “divorce” Move Forward if it wants support from the Senate to form a government.