Varanon Peetiwan lost his job as director-general of the Employment Department not because of a tainted track record but over his slow response to labour policies that were sometimes beyond his power to deliver, according to a source at the Labour Ministry.
With a year left before retirement, Mr Varanon was suddenly transferred out as department chief to deputy labour permanent secretary, a post technically higher up the ladder but which carries little real decision-making authority.
The transfer was signed by Prime Minister Prayut Chan-o-cha on Wednesday in an order under the powerful Section 44 which was carried over from the previous charter.
Mr Varanon admitted he did not see the transfer coming, saying he did not know the reason for shifting him. He also thought using Section 44 to sideline him was unnecessary.
Mr Varanon, according to the source, comes across as a straightforward person with no dubious working record.
However, complex labour problems have arisen involving the employment of illegal migrant workers in many export industries including fisheries. The government has come under heavy pressure from the US and the EU, Thailand's main export markets, to systematically root out the problems or risk facing trade sanctions.
According to the source, what might have cost Mr Varanon his job is thought to be persistent allegations of kickbacks paid to labour officials by employers in the registration of migrant workers.
It was alleged the bribes paid were in the region of 5,000 to 80,000 baht per worker.
Employers were willing to offer bribes to avoid a tedious labour registration procedure, said the source.
Despite Mr Varanon's insistence that he did not receive any kickbacks, he could not avoid responsibility for malpractices under his watch, according to the source.
The slow registration process in verifying migrant workers' nationalities was blamed in part on red tape that exists in countries of origin conducting verification work.
The source said the department declined a role in the verification which is the responsibility of the origin countries for fear of being the target of malpractice accusations.
Verification officially began on Aug 8, which called for origin countries to set up checking centres in Thailand to process their own nationals. However, opening some centres was delayed.
So far, only about 50% of 1.9 million migrant workers from Myanmar, Laos and Cambodia have had their nationalities verified.
A more effective and faster method was proposed by the government using retina scans.
However, Mr Varanon thought a study was needed first to determine cost effectiveness, the source said.
Time was not on the government's side as the EU is pressing Thailand to declare the number of migrant workers it has registered so as to separate legal from illegal workers.
Mr Varanon may also have upset the prime minister for supporting stiff fines against employers hiring illegal migrant workers, ranging from 400,000 to 800,000 baht, the source said.