I think it's fair to say there has been a tendency on the part of tThai authorities to accept statistics that did not fully reflect the death toll. Thais died quietly at home and families were reluctant to allow Covid to be declared a cause of death.

On the other hand "deaths within x days of a Covid diagnosis" was the general criterion for recording a Covid death in europe. So we have one system underestimating direct Covid deaths, the other over-estimating them. The degree of over/over estimation is moot.

It seems clear the sensible assessment of the impact of the pandemic will be excess deaths - mortality above the expected level. This will include those who died because of cancelled operations, delayed diagnosis for cancer and other serious conditions etc.

Thailand appear to have been caught in similar attack of over-confidence as India. India believed it had beaten the virus, Thailand believed it had largely avoided it. Both countries have been lazy on the vaccine front; both were careless about lockdowns. The difference is that disease appears to be out of control in India, while Thailand might be able to stifle it by taking decisive steps to tackle it.