Thailand has moved up 17 places to 85th in the 2014 Corruption Perceptions Index rankings from 102nd in the previous year.
However, the score, at 38 this year, improved only marginally from 35 and 37 places in 2013 and 2012 respectively. The score of 0 is highly corrupt and 100 very clean.
More than two thirds of the 175 surveyed countries scored below 50.
In the data released by Transparency International on Wednesday, Denmark continued to lead with a score of 92 while Somalia and North Korea tied at the other end of the scale at 174th, with a score of 8.
The biggest falls were in Turkey (minus-5), Angola, China, Malawi and Rwanda (all minus-4) while the biggest improvers were Côte d'Ivoire, Egypt, Saint Vincent and the Grenadines (+5), Afghanistan, Jordan, Mali and Swaziland (+4).
"The 2014 Corruption Perceptions Index shows that economic growth is undermined and efforts to stop corruption fade when leaders and high level officials abuse power to appropriate public funds for personal gain,” said José Ugaz, the chair of Transparency International.
Asia-Pacific needs work
Of 28 countries in Asia-Pacific, which account for 61% of the world's population, 18 scoring less than 40 out of 100.
The scores are "a resounding message to leaders that, despite many public declarations and commitments, not enough is being done to fight corruption", Transparency International wrote in the summary.
"The persistent low scores ask a critical question to the leadership of Asian countries, which have full control of the conduct of its public services." For China and India, two countries where new leadership are pursuing anti-corruption drives, "the index is a harsh reality check".
China shows a downward trend in the index (with a score of 36) in comparison to last year (40).
Together with India (38) and China (36), the poor scores of other emerging markets in the region — such as Malaysia (52), Philippines and Thailand (both 38) and Indonesia (34) — indicate a general weak or ineffective leadership to counter corruption, posing threats for both sustainability of their economies and somewhat fragile democracies.
The index is based on expert opinions of public sector corruption. Countries’ scores can be helped by open government where the public can hold leaders to account, while a poor score is a sign of prevalent bribery, lack of punishment for corruption and public institutions that don’t respond to citizens’ needs.