The source reportedly said Thaksin was in Beijing, China, during the Songkran Festival.
A number of former Pheu Thai Party MPs, former and caretaker cabinet ministers and close associates flew to Beijing to pay him a visit and discuss the political situation in Thailand, the source said.
Thaksin expressed concern about developments. Expecting the situation could turn violent, he sent a signal that the red-shirts should avoid a direct confrontation with their opponents, the reports said.
However, Thaksin reportedly said the red-shirts could demonstrate to show their strength because people in society would not accept rulings by independent organisations on cases against caretaker Prime Minister Yingluck Shinawatra if the decisions were pre-determined.
According to the source, Thaksin believed there was a high chance of a coup after the Constitutional Court delivers its ruling on the case against the caretaker prime minister and the cabinet.
The coup would not be led by Gen Prayuth Chan-ocha, the army chief, but by another man being sought out by a former influential general of the Eastern Forces, or Burapa Payak, according to Thaksin.
The former prime minister expressed sympathy for his sister, Ms Yingluck, having to withstand such pressure.
Thaksin was quoted as saying to close associates who visited him that: "If all parties concerned return justice to the country, members of the Shinawatra family would be willing to quit politics. If the situation is allowed to continue like this, it will likely turn violent."