The People's Democratic Reform Committee (PDRC) leader apologised to supporters on his Facebook page, telling them the dinner scheduled for Saturday would be cancelled. He said future weekly dinners would be called off as well but did not give any reason.
The message was posted shortly after Gen Prayuth made his weekly televised address on Friday, in which he warned against any further "political" talk that could reignite social conflict.
The coup leader did not name Mr Suthep but he was known to have been furious after the former Democrat Party power-broker boasted at a fund-raiser last weekend that he had been in regular contact with the army chief.
Mr Suthep had been planning a series of "Dinner with Lung Kamnan" events, starting with the June 21 dinner, to raise funds for protesters and their families injured or killed during the street rallies against then-prime minister Yingluck Shinawatra.
In his address on Friday night, the chief of the National Council for Peace and Order (NCPO) made clear that no more such events would be tolerated. They disrupted plans to end political rifts and could only encourage rival political factions to follow suit, he said, warning of action if his message is ignored.
"I did not collude with anybody," he said in apparent response to Mr Suthep's claims. Rather, the deterioration of the political situation forced the army to resolve the problem by staging the May 22 coup, he said.
"Stop it here. Don't organise events like political talks and dinners to raise funds to help anybody. It's not the right time to do that," Gen Prayuth added.
It is unclear where Mr Suthep is. He returned to his home province of Surat Thani on Wednesday for the first time since he began leading the protests in the capital in late October.
Mr Suthep told the inaugural fundraising dinner at Bangkok's posh Pacific City Club that his movement had spent 1.4 billion baht over six months. He said 400 million came from the families and allies of protest leaders and 1 billion from cash donations from supporters. A more precise accounting of the spending has not been made available.
Guests at the June 21 dinner donated money to a fund to establish the new foundation, which Mr Suthep insisted would not be political in nature.
Mr Suthep and other PDRC leaders raised eyebrows earlier when they staged a party just days after the coup, at which many participants wore military-style attire.
That prompted an NCPO spokesman to declare that wearing camouflage shirts and similar gear was not appropriate for civilians in light of current circumstances.