Thai PM Yingluck Shinawatra this afternoon became the first Thai leader in nearly two decades to meet Britain’s monarch, in an audience at Buckingham Palace. According to an article in the Financial Times, neither Abhisit not Thaksin met with Queen Elizabeth during their official visits to England as prime ministers. The British monarch herself paid two official visits to Thailand, in 1972 and 1996.
UPDATE: After a couple of people refuted the claim in the FT that Yingluck was the first Thai PM in decades to have an audience at Buckingham Palace I did another Google search and found this picture:
That is Abhisit in the back row. Queen Elizabeth hosted a reception for G20 leaders at Buckingham Palace in April 2009. I believe he was there representing ASEAN as that year Thailand was holding the chair. As far as I know, he didn’t receive a private audience with the Queen as prime minister of Thailand. If anyone knows anything different then please let me know.