The stories related to two expatriate Scots involved in the sex industry.
Drummond has been cleared of two counts of criminal libel brought by James Lumsden, 59, from Falkirk, and Gordon May, 67, from Edinburgh - two businessmen involved in the sex industry in the resort of Pattaya.
Legal action was brought against Drummond after he wrote a series of articles describing the misfortunes that befell Britons who went into business with Lumsden and May.
In April 1990, Iain Macdonald, 28, died in a fire at the Ambiance Hotel in Pattaya. A second businessman Kevin Quill, 39, from Bradford, Yorkshire, invested money with May and Lumsden and was jailed for six years for drug possession after he was arrested by police in 2000.
The Appeal Judges, Seramee Sirimankarak, Sittisak Wanachkij and Ariya Navintum ruled: "The defendant was doing his job as a journalist, making facts public for foreigners doing business in Thailand. There is nothing defamatory in what he wrote."
Marwaan Macan-Markar, president of the Foreign Correspondents' Club of Thailand, said: "We welcome these two court rulings in favour of Andrew Drummond, particularly since the alleged libels involved were criminal offences under existing Thai law.
"The verdicts demonstrate a fundamental respect for investigative reporting in the public interest. This is a good day for journalism and the law in Thailand."
The original reports were printed in London and Glasgow but Lumsden chose to sue in Thailand, which he considered his home, after the Bangkok Post printed similar stories. Drummond was subsequently given two two-year suspended prison sentences.
Drummond said: "I'm of course very pleased. But this is small consolation for the families of Iain Macdonald or Kevin Quill. Their lives have been devastated.
"My thanks must go to Steve Turner former president of the BAJ for his never ending support and encouragement and my colleagues on newspapers in the UK and their bosses who helped pay my expenses."
Andrew Chant writes for Press Gazette.