Deputy Prime Minister Prawit Wongsuwon's trip to London last week has sparked speculation he may have secretly met ousted prime minister Thaksin Shinawatra.
Gen Prawit, who also serves as defence minister, was in the British capital from Tuesday to Friday. Thaksin's daughter Pintongta posted a picture with her father in London on Saturday.
The visit, made in response to an invitation by his British counterpart, was Gen Prawit's first overseas trip since former prime minister Yingluck Shinawatra fled Thailand to avoid a court judgement.
Her escape raised questions about whether the National Council for Peace and Order (NCPO) secretly helped her escape.
Ms Yingluck failed to show up at the Supreme Court's Criminal Division for Holders of Political Positions on Aug 25 to hear a ruling on that day in her rice pledging case.
The doubts have lingered despite vehement denials by Prime Minister Prayut Chan-o-cha, Gen Prawit and army chief and NCPO secretary-general Chalermchai Sitthisad and in spite of their assurance Ms Yingluck was capable of fleeing on her own, without the NCPO's help.
Ms Yingluck's whereabouts are still unknown, as the court prepares to hand down its ruling at a rescheduled hearing on Sept 27.
Meanwhile, the Department of Special Investigation has been stepping up its probe against Panthongtae Shinawatra, Thaksin's son, and three other people who allegedly received part of a fraudulent Krungthai Bank (KTB) loan for 9.9 billion baht related to the KTB scandal that took place from 2003-2004 under the Thaksin government.
Receiving assets from a corrupt scheme forms the basis of money-laundering under Thai law.
Critics asked whether Gen Prawit and Mr Thaksin might have discussed these issues, or even Mr Thaksin's political role and the idea of a so-called government for national reconciliation under Gen Prayut's premiership.
Gen Chaichan Changmongkol, the permanent secretary for defence, who left for the same London trip slightly later than Gen Prawit, dismissed speculation Gen Prawit had met Mr Thaksin in London.
Gen Chaichan said Gen Prawit's trip to London had nothing to do with Ms Yingluck either, insisting the trip was made in response to the invitation by the British defence minister.
But rumours persist that a rich man with close ties to Pheu Thai joined the delegation specifically to ensure Gen Prawit the visit went smoothly.
A source close to Gen Prawit said there was no reason for the deputy prime minister to go all the way to London to hold talks with Thaksin because he could always make contact over the phone or via video call if he really wanted to get in touch.
A source close to Gen Chatchalerm Chalermsuk, an adviser to Gen Prayut who travelled to London ahead of Gen Prawit, said Gen Chatchalerm had begun working with his British counterparts on the proposed trip a long time ago and the itinerary had nothing to do with any secret deal or Mr Thaksin.
The source insisted Gen Prawit and Mr Thaksin didn't meet during the trip as alleged.
A firm denial of any meeting or negotiations also emerged from defence spokesman Kongcheep Tantravanich who insisted he was with Gen Prawit throughout the trip and there was nothing for Gen Prawit and Mr Thaksin to negotiate about.
"Being in England at the same time doesn't mean the two saw each other," said Maj Gen Koncheep. "There is absolutely no reason for them to meet."
He further denied rumours the defence minister's UK visit involved the striking of a political deal with Thaksin, including the negotiation of asylum seeker status for former prime minister Yingluck Shinawatra.
Maj Gen Kongcheep said Gen Prawit's UK visit had a tight itinerary, involving meeting his British counterpart and Minister of State for Asia and the Pacific, Mark Field.
"The itinerary was so packed that it left no room for an unscheduled meeting," said Maj Gen Kongcheep.
Samart Kaewmeechai, a former Chiang Rai MP and a key member of Pheu Thai, told the Bangkok Post: "We have to believe Gen Prawit who has already said they they did not meet."
He added he did not hear any news about their meeting and did not hear any news from Mr Thaksin.