Having taught at government and private schools I echo the frustration of native English teachers when it comes to Thais being poor in English. I had been queried by the Ministry of Education once as to remedies. I made these recommendations:
1) Lead from the top to the bottom. This means enforce the laws and rules from the national to the provincial and school levels.
a) Cease the 'No student fails" philosophy and make it plain to the parents and students it is by their individual efforts where they will pass or fail in class.
b) Get the parents involved in the education through regular parent-teacher meetings. These meetings should be where the parents are shown the students performance in the records of grades in class performance and participation.
c) Use the Thais desire to play games to learning experiences. Incentivise the participation of the students and keep records
2) The funding from the national office should not be dog robbed to the pockets of the school administrators. Truly designate separate funding for teacher, school administration, and classroom supplies salaries.
a) Pay the teachers for demonstrated and recorded performance. Scale the pay to training, years experience and performance.
b) prosecute the administrators at provincial and school levels who pocket the 'extra' funds designated for teacher salaries
3) Drop the 'save face' attitude in lessons. Effectively teach when asked a question listen, understand the question and answer the question. Do not just say 'yes' . Saving 'face' by telling the questioner any answer without understanding the question is not acceptable to a NES. This is going to be a battle of Thai culture and asian custom with NES culture and custom. It will force a different frame of mind thinking process.
4) Go on a sincere and honest teacher search recruitment outside of Thailand with emphasis on finding master teachers who could take sabbaticals to teach in Thailand for 1-3 yrs.
Make the criteria for selection be degrees in science, mathematics and humanities from Canada, America, England, Australia, New Zealand and the Philippines. Then when hired place them with schools and teachers in the schools, province offices and national office who really speak English to work as a team to produce curriculum at the appropriate level.
Push the curriculum from the schools up the chain of command. Supply them with housing appropriate to the standards the teacher left.
5) Most important, communicate without intimidation. Lead with honesty by example from the top. Nothing will get or gain support and cooperation for these policy and cultural changes than honest sincere leadership from the top of the chain of command down through the provinces to the schools and classroom.