The 2015 Programme for International Student Assessment (Pisa) shows sharp falls in maths, sciences and reading scores for students in Thailand.
Thai students are underperforming their peers in several Asian countries as their scores were below the international average in all three subjects.
Pisa, which is funded by the Organisation for Economic Cooperation and Development (OECD), surveyed the knowledge and skills in mathematics, sciences and reading of more than half a million 15-year-olds across 70 countries worldwide. The evaluation takes place every three years. Thailand has participated in the evaluation since 2000.
According to the survey released on Tuesday, Thailand ranked 54th for maths, 57th for reading, and 54th for sciences.
Thai children scored 415 points in maths, far lower than the international average of 490 points. In sciences, Thai students scored 421 points, much worse than the international average of 493. And in reading, Thais scored 409 points, well below the OECD average of 493 points.
Acting Education Minister Teerakiat Jareonsettasin said Thailand's performance in reading and sciences has dropped sharply from 2012 when students scored 444 points in sciences and 441 in reading.
However, the country's maths performance has only deteriorated by 12 points since the last evaluation.
Red circles show the Thai standing against the world in, from left, overall ranking, in science, and in reading and maths. (Source: PISA 2015 Results)
Standing at 54th, Thailand's overall performance is far below other Asian countries. Singapore was the top performer in all three subjects in the Pisa tests, followed by Japan in second place, Taiwan in fourth, China in sixth, while Vietnam did well at eighth.
Finland, Estonia, Canada and Ireland were the only non-Asian countries to get into the top 5 in all three subjects.
Athapol Anunthavorasakul, an academic from Chulalongkorn University's faculty of education, said the Pisa results show Thailand is failing to improve its education quality.
"In the past two to three years, the Education Ministry has invested money trying to get better results in the Pisa test. It trained many teachers and students for the latest global snapshot of student performance, but our country is still lagging behind leading countries in education and has made no progress at all in international rankings," he said.
However, Mr Athapol said Pisa alone does not truly reflect the academic ability of all Thai students because what Pisa measures is not the accumulation of information and knowledge as traditional academic tests do, but how children can apply themselves to solve issues they are likely to face in the real world.
"In 2012, we allowed students from the demonstration schools and Princess Chulabhorn college schools [to take part in the Pisa test] and that is why we saw a slight improvement in Thai scores. But I think this time students in these schools may not have taken part, so our scores dropped again," he said.
Mr Athapol said Pisa results indicate serious disparities between students in well-known schools and students in rural areas.
Therefore, he suggested that the Education Ministry try to narrow this gap, not just climb international rankings.