Thailand former minister Thaksin Shinawatra has left the United States without fanfare.

A phone-in was made to his supporters from South Korea, signalling an end to the US visit, which was marred by questions over whether US authorities ignored their own law, and by the return of the WikiLeaks ghost to haunt Washington.

The United States' permission for Thaksin Shinawatra to enter the country, now that his party's in power, has put the superpower's diplomacy under scrutiny. Critics pointed to the WikiLeaks-exposed documents that purportedly showed the US Embassy in Thailand once considered him a man unsuited for a US visa. The alleged embassy cable statement claimed Thaksin "may or may not have committed crime of moral turpitude" following the street turmoil in 2009 when the Democrats were in power.

Anti-Thaksin Thais have staged protests both in Thailand and the United States. Complaint letters were written to American authorities including Secretary of State Hillary Clinton.

Thaksin has admitted that US authorities did not want him to visit their country when the Democrats were in power.

The US authorities also became concerned about possible repercussions of his visit, so much so he was advised to keep a low profile and quietly leave the country. The reports could not be verified.