Nine firms from countries including China, India, Germany and the Netherlands are set to join an online tender in April to supply the tablet computers, according to the Ministry of Information and Communication Technology (ICT).
"This will be the world's largest amount of tablets given away by a government for education," said Surapol Navamavadhana, a government advisor involved in the "One Tablet Per Child" scheme.
"This is the touch era. Whatever children do, they want to touch things", he told AFP.
With each tablet expected to cost roughly $100, the total value of the orders looks set to be worth more than four billion baht ($140 million).
They will be given to primary students aged about six years old as well as to middle-school students aged between 12 and 13 years, along with 54,000 tablets to be given to teachers.
The ruling Puea Thai party, linked to fugitive former Thai premier Thaksin Shinawatra, pledged to issue free handheld computers to students as one of a raft of pledges that helped it to election victory in 2011.
The party -- led by Thaksin's sister Yingluck Shinawatra -- has been accused by the opposition of populism over its election promises.
About 850,000 tablets were already given to students last year, supplied by China's Shenzhen Scope Scientific Development Co. at a cost of about about 2.2 billion baht ($75 million).
Next year the government aims to distribute a further seven million tablets, according to the ICT ministry.
The tablets will remain the property of the schools for three years, during which time the students can take them home each day. After that the students will own them.
But the authorities is calling on teachers and parents to ensure that students do not stay glued to the screens for too long.
"Students should not use the tablets for more than two hours per day otherwise they won't be able to differentiate between textbooks and tablets," said Soratda Phumwiphat, another advisor involved in the scheme.