Thailand's corruption situation has eased because a "people's network" has closely monitored irregularities and the military-installed government has vowed to tackle the problem seriously.

The latest survey by the University of the Thai Chamber of Commerce (UTCC) found that bribe payments by businesses to state officials and politicians last month declined to 5-15% of project value or 50.3 to 150 billion baht.

The previous survey last June reported kickbacks equal to 15-25% of project value or 150-251 billion baht. Government spending was worth 2.5 trillion baht for all of last year.

Thanavath Phonvichai, vice-president for research and director of the UTCC Center for Economic and Business Forecasting, said the latest figure was the lowest in five years.

That compared with 25-35% on average from 2010-13, which cost the country at least 325 billion baht.

Tea money is the most common form of corruption.

"Based on the latest survey, we've found businessmen, state officials and politicians alike dared not pay or accept bribes due to a growing people's network in monitoring corruption. More importantly, the government has made a commitment to tackle the problem of corruption," Mr Thanavath said.

"The improvement is a good sign, as the government could use such money to stimulate the economy.

"With the government's economic stimulus measures including infrastructure development and falling oil prices, we expect the economy will grow by 3-4% this year as expected."

UTCC president Saowanee Thairungroj said the corruption situation index (CSI), which was based on 2,400 respondents in the business and government sectors and state officials nationwide, improved to 49 points last month from 46 points in June.

The index that gauges the current corruption situation also improved to 47 points from 45, while that on the corruption situation outlook stands at 50 from 46.

The closer a CSI score is to zero, the higher the level of corruption, while 100 shows high transparency and a lack of graft.

Ms Saowanee said the most important factors behind widespread corruption in Thailand were indecisive law enforcement, the lack of an effective mechanism to supervise and inspect corruption practices and a lack of ethics among companies.

State bureaucracy, a lack of political transparency, low remuneration to state officials, lucrative political benefits and long-standing practices of bribery payments were also part of the corruption problem.